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VALIDATION AND OPTIMAZATION OF OPTICAL RULES

FOR C-WDM ACCESS NETWORK

A

Thesis Report

Submitted to

The Department di Elettronica, Informazione e Bioingegneria

POLITECNICO DI MILANO, MILANO, ITALY

In partial fulfilment for the award of degree of

MASTER OF SCIENCE

IN

ELECTRONICS ENGINEERING

Supervisor:

Prof. Mario Martinelli

Co-Supervisor:

Ing. Rosanna Pastorelli

Submitted By:

Naveen Joon 10486043

Department di Elettronica, Informazione e Bioingegneria

Politecnico di Milano, P.zza L. da Vinci, 32, 20133 Milano, Italy

APRIL 2017

Contents

Abstract (English and Italian) ………….………………………………………………………xii-xiv

1. INTRODUCTION & MOTIVATION 1.1. INTRODUCTION ........................................................................................................................... 1

1.1.1 Origin of C-WDM ...................................................................................................................... 5

1.1.2 Features of C-WDM .................................................................................................................. 7

1.1.3 Access Network………………………………………………………………………………. 8

1.2. MOTIVATION ................................................................................................................................ 9

1.3. ADVANTAGES & DISADVANTAGES OF CWDM.................................................................. 10

1.3.1 Advantages ............................................................................................................................... 10

1.3.2 Disadvantage ............................................................................................................................ 11

1.4. APPLICATION ............................................................................................................................ 11

1.5. ORGANIZATION OF THESIS.................................................................................................... 12

2. OPTICAL RULES FOR CWDM NETWORKS 2.1 NETWORK REQUIREMENTS ..................................................................................................... 13

2.1.1. Network Topology .................................................................................................................. 13

2.1.2. Optical Fibre ........................................................................................................................... 14

2.1.3. Oadm/F-Oadm ........................................................................................................................ 15

Certificate ……………………………………………………………………………………….……....i

Acknowledgement …………………………………………………………..…………………….…. ii

Declaration by Scholars …………………………………………………...……………………...…. iii

List of Abbreviations ……………………………………………………..…………………………...iv

List of Symbols ………………………………………………………….……………………..……. vii

List of Tables ……………………………………………………………………………………….... ix

List of Figures …………………………………………………………………………………….…...x

2.1.4. MUX/DEMUX with or without upgrade port ......................................................................... 18

2.1.5. Optical Bypass ....................................................................................................................... 20

2.1.6. Pluggable Trans-receiver module .......................................................................................... 21

2.1.7. Connectors Identifier .............................................................................................................. 22

2.2 OPTICAL RULE FOR DESIGN OF CWDM NETWORK ........................................................... 23

2.2.1 Optical Rule ............................................................................................................................. 24

2.2.2 Optimization of Cost of Network ............................................................................................. 29

2.2.3. Finding the No. Of Overlapping/Common Node in Different Connections ........................... 29

2.3. OPTICAL IMPAIRMENTS & POWER BUDGET ...................................................................... 32

2.4. LOSSES IN ACCESS NETWORK ............................................................................................... 33

2.4.1. Worst Case Approach ............................................................................................................. 33

2.4.2. Statistical Approach ................................................................................................................ 39

3. ALGORITHM FOR OPTIMIZATION OF NETWORK 3.1. ALGORITHM FOR OPTIMIZATION OF NETWORK WITHOUT

OPTICAL BYPASS & WITH CHANNEL UPGRADE-ABILITY ..................................................... 43

3.1.1. Network topology with The Output of the MATLAB ............................................................ 46

3.2. ALGORITHM FOR OPTIMIZATION OF NETWORK USING OPTICAL BYPASS & COST

OPTIMIZATION WITH CHANNEL UPGRADE-ABILITY CONSTRAINTS ................................. 51

3.2.1. Network Topology with The Output of the MATLAB ........................................................... 55

3.3 USING PROTECTED PATH IN LINEAR TOPOLOGY .............................................................. 59

3.4 USING ALL OADM NETWORK WITH RING TOPOLOGY ..................................................... 62

3.4.1. Received Power at Uplink & Downlink ................................................................................. 63

3.5 KEY FEATURES OF ALGORITHM ............................................................................................ 65

4. CONCLUSION & FUTURE SCOPE 4.1. CONCLUSION ............................................................................................................................ 67

4.2. FUTURE SCOPE ......................................................................................................................... 68

4.2.1. 1-Channel To N-Channel ........................................................................................................ 68

4..2.2. From Cwdm To Dwdm .......................................................................................................... 69

4.2.3. From Access To Larger Network ............................................................................................ 69

4.2.4. Lab Activity ............................................................................................................................ 69

4.2.5. Developing Software……............................................................................................................70

5. REFERENCES Reference………………………………………………………………………………………………….71

6. APPENDIX Appendix A………………………………………………………………………………………………..72

Appendix B………………………………………………………………………………………………..75

Appendix C………………………………………………………………………………………………..78

Appendix D………………………………………………………………………………………………..88

[i]

POLITECNICO DI MILANO

P.zza L. da Vinci, 32, 20133 Milano, Italy

Phone: 800.02.2399 Fax: +39.02.2399.2206

Website: www.polimi.it

CERTIFICATE

This is to certify that “Naveen Joon (10486043)” students of Telecommunication

Engineering from “POLITECNICO DI MILANO, ITALY” has done their Thesis at

“SM Optics.srl, Milano, ITALY” in the partial fulfilment for the award of degree of

“Master of Science” under the guidance of “Prof. Mario Martinelli” and “Ing.

Rosanna Pastorelli”.

The project work entitled as “optical rules for C-WDM network validation and

optimization ” embodies the original work done for Thesis. This work has not been

submitted partially or wholly to any other university or institute for the award of this or

any other degree.

Prof. Mario Martinelli

The Department di Elettronica, Informazione

e Bioingegneria.

Ing. Rosanna Pastorelli

Prooject Manager

SM Optics s.r.l.

http://www.polimi.it/

[ii]

ACKNOWLEDGEMENT

I would like to thank all those who gave us the possibility to complete this Thesis. I want

to thank the Department di Elettronica, Informazione e Bioingegneria of

“POLITECNICO DI MILANO” and “SM Optics s.r.l.” for giving me such a golden

opportunity to commence this Thesis in first instance. I express our deepest gratitude to

“Prof. Mario Martinelli” who encouraged me to go ahead with Thesis. It is a matter of

pride and privilege for us to complete our dissertation under his supervision.

We are also very grateful to Ing. Rosanna Pastorelli, from SM Optics for the facilities

and cooperation, she provided me guidance in the completion of Thesis work. I also

express our deepest gratitude to “Ing. Rosanna Pastorelli”. Whatever is said in the

praise of Ing. Rosanna Pastorelli is not enough, her soul touching humility, her straight

forward attitude, her methodological approach, her eagerness to share her wisdom, her

aim for perfection and her never ending encouragement and patience are but a few of her

noble qualities. Our special appreciation goes to teachers, who has inspired and guided us

during two years in this institution by their brilliant and expert teaching. We gratefully

acknowledge the help and cooperation extended by the library staff of the faculty as well

as university. Our heart gratitude goes to our parents and all friends for their invaluable

inspiration extended in the pursuit of this work.

………………………

Naveen Joon

[iii]

DECLARATION BY SCHOLAR

I hereby declare that the work reported in my M.Sc. thesis entitled as “Optical rules

for C-WDM network validation and optimization” submitted at Department di

Elettronica, Informazione e Bioingegneria, Politecnico di Milano, is an authentic

record of our work carried out under the supervision of prof. Mario Martinelli and Ing.

Rosanna Pastorelli. I have not submitted this work elsewhere for any other degree.

……………………………..

Naveen Joon

(836254)

http://magarini.faculty.polimi.it/

[iv]

List of Abbreviations

S.No. Abbreviation Description

1. CWDM Coarse Wavelength Division Multiplexing

2. DWDM Dense Wavelength Division Multiplexing

3. MUX Multiplexer

4. DeMUX DeMultiplexer

5. OADM Optical add drop multiplexer

6. F-OADM Fix-Optical add drop multiplexer

7. Gbit Giga bit

8. Gbps Giga Bit per Second

9. GBIC GigaBit Interface Converter

10. ADSL Asynchronous Digital Subscriber Line

11. VDSL Very High-speed Digital Subscriber Line

12. GSM Global System for Mobile communication

13. UMTS Universal Mobile telecommunication System

14. LTE Long Term Evolution

15. Wi-Fi Wireless Fidelity

16. WiMAX Worldwide Interoperability for Multiple Access

[v]

17. OLT Optical line Terminal

18. CO Central Office

19. ONT Optical Network Terminal

20. ITU International Telecom Union

21. MAN Metropolitan area Network

22. LAN Local Area Network

23. SAN Storage Area Network

24. SFP Short Form-factor Pluggable

25. SDH Synchronous Digital Hirarchy

26. PON Passive Optical Network

27. MSA Multi Source Agreement

28. OTU Optical Transport unit

29. LED Light Emitting Diode

30. SONET Synchronous Optical Network

[vi]

List of Symbols

S. No Symbols Description

α0 Upper level of “0”

α1 Lower level of “1”

A Attenuation

D Chromatic dispersion coefficient

C Connection set

K Wavelength set

λ wavelength(s)

L Link length

n no. of express nodes

ε Cross talk value

[vii]

List of Tables

S. No. Table no. Title of the Table Page No.

1. Table-1.1 Wavelength band used in CWDM. 7

2. Table-2.1 Wavelength specification of 1x2 channel OADM pin 17

3. Table-2.2 Performance specification of 1x2 channel OADM pin. 18

4. Table-2.3 Wavelength specification of 1x8 channel MUX pin. 19

5. Table-2.4 Traffic matrix of network containing six connection. 31

6. Table-3.1 traffic matrix for seven connection of a network. 47

7. Table-3.2 traffic matrix for seven connection of a network. 56

List of Figure

S. No. Figure no. Caption of the Figure Page No.

1. Fig.1.1 Attenuation and dispersion coefficient curve w.r.t.

wavelengths.

8

2. Fig.1.2 Example of passive optical network. 9

3. Fig.2.1 Linear topology. 13

4. Fig.2.2 Ring with hub topology. 13

5. Fig.2.3 Geometry of Optical fiber 14

6. Fig.2.4 1X2 channel OADM in both east and west direction.

16

7. Fig.2.5 8-channel Mux/DeMux without upgrade pin.

18

8. Fig.2.6 16-channel Mux/DeMux with upgrade pin.

19

9. Fig.2.7 Optical bypass. 20

10. Fig.2.8 Type of Connectors used between fiber cable and

components.

22

11. Fig.2.9 Connection with one common node. 25

12. Fig.2.10 Connection with no common node. 26

13. Fig.2.11 Installation of OADM with colour allocation for case1. 26

[viii]

14. Fig.2.12 Installation of OADM with colour allocation for case 1. 26

15. Fig.2.13 Connection with more than one common node. 27

16. Fig.2.14 Allocation of wavelength with optical bypass. 27

17. Fig.2.15 Installation and allocation of wavelength if channel

requested is more than 1. by any of the connection.

28

18. Fig.2.16 Access Network for CWDM using passive elements such

as OADM & Mux/DeMux.

30

19. Fig.2.17 Considering the ring topology as linear network presenting

connections.

31

20. Fig.3.1 Algorithm for finding optimized solution by cascaded

nodes & without using optical bypass.

45

21. Fig.3.2 A CWDM passive network with seven connections. 46

22. Fig.3.3 Linear presentation of network. 47

22.

Fig.3.4 Received power (in dBm) at each connection for all the

available 16 wavelengths in uplink direction is shown

below by a plot.

48

23.

Fig.3.5 Received power (in dBm) at each connection for all the

available 16 wavelengths in downlink direction is shown

below by a plot.

49

24.

Fig.3.6

Solution of network with linear configuration.

49

25. Fig.3.7 Graph presenting the wavelength used per span of the

network.

50

26. Fig.3.8 Algorithm for finding optimized solution using optical

bypass & cascaded nodes.

54

27. Fig.3.9 A CWDM passive network with six connections. 55

[ix]

28. Fig.3.10 Received power at each connection for all the available 16

wavelengths in uplink direction is shown below by a plot.

56

29. Fig.3.11

Received power at each connection for all the available 16

wavelengths in downlink direction is shown below by a

plot.

57

30. Fig.3.12

Solution of given network with linear configuration.

58

31. Fig.3.13

Graph presenting the wavelength used per span of the

network.

58

32. Fig.3.14

Link length with 1,2,3…,8 OADM nodes in network.

59

33. Fig.3.15

Network length with 1,2,3…,8 OADM nodes in network.

60

34. Fig.3.16

A CWDM passive network with TS-Node connections

only.

61

35. Fig.3.17

A CWDM passive network with All-Oadm nodes in

network.

62

36. Fig.3.18

Linear presentation of All Oadm network.

62

37. Fig.3.19

Received power in uplink direction.

63

38. Fig.3.20

Received power in uplink direction.

63

39. Fig.3.21

Solution of given network in linear configuration. 64

40. Fig.3.22

Wavelength used per span of the network.

65

[xi]

ABSTRACT(ENGLISH)

Optical rules for C-WDM 10 gbps channels network validation and optimization using passive optical

devices such as 2-channel fixed OADM,4-channel fixed OADM ,1x8 MUX/DEMUX and 1x8

MUX/DEMUX with upgraded pin is analyse in this Thesis. In this Thesis, network rules are designed

for C-WDM network using of the passive devices and optical bypass for the optimization of network

in terms of efficiency, cost and capacity. In the first release of the access network, optimization is

done without using an optical bypass and hence it forces us to made use of cascade node at OADM

place in the ring. In the second release of the network we are using optical bypass which in return

reduces the efficiency but increase the optimization area in terms of cost of the network. Two

algorithms are proposed based on different scenario.

Software used for the analytical and verification is MATLAB R2014a/2015a and octave which is free

software like MATLAB. Using this software, all the losses, power expressions were plotted and

analytical results were matched with optimization rules proposed during project.

ABSTRACT(ITALIAN)

In questa tesi sono state sviluppate le regole ottiche per la validazione e l'ottimizzazione di una rete

di accesso C-WDM, con canali modulati a 10Gbps, contenente dispositivi ottici passivi come OADM

fissi a due canali, OADM fissi a quattro canali, 1x8 MUX/DEMUX e 1x8 MUX/DEMUX con porta

di upgrade. L'ottimizzazione è stata implementata per massimizzare efficienza e capacità e

minimizzare i costi. La rete sotto analisi contiene fino a cinque nodi OADM, a due o quattro canali,

ed un hub (nodo senza traffico ottico espresso), realizzato con MUX/DEMUX. Vengono presentati

due possibili scenari: nella primo, l'ottimizzazione dell'anello della rete di accesso è stata

implementata utilizzando una cascata di OADM nello stesso nodo; nel secondo, viene utilizzata la

tecnica del bypass ottico, che riduce l'efficienza, ma aumenta le possiblità di ottimizzazione in termini

di costo. Per entrambe le possibilità, sono stati sviluppati dei relativi algoritmi di ricerca della

soluzione ottima.

I software utilizzati per l'analisi ed il calcolo sono MATLAB R2014a/2015a e GNU Octave, impiegati

per simulare il contributo delle perdite ottiche di linea e per la soluzione dei problemi combinatori

durante la ricerca della soluzione ottima.

Department di Elettronica, Informazione e Bioingegneria Politecnico di Milano, P.zza L. da Vinci, 32, 20133 Milano, Italy.

1

CHAPTER-1 INTRODUCTION & MOTIVATION

This chapter consists of: the introduction of Thesis objective and contribution, motivation

behind endorsing CWDM instead of SONET/SDH along with pros and cons of using CWDM

in access network. It explains the idea behind using CWDM in replacement of SONET/SDH.

1.1 INTRODUCTION:

When observing traditional SONET, the next generation of WDM (Wavelength Division

Multiplexing) is seen as a simple architecture, with scalability, high capacity add/drop, multiple

ring terminations, multi-services, higher Bandwidth and multiple fabrics. At the same time,

WDM Equipment is increasingly showing its viability in the current networks with tremendous

available bandwidth over the existing fiber plant, along with a variety of service interfaces and

superior optical transmission capabilities. A new generation of apparatus is also being

presented that provides options that come with both SONET and WDM. Some are WDM

systems with integrated SONET units that provide grooming, add/drop and protection of the

wavelength. Others are built in WDM capability that offer optical multiplexing, amplification

and transmission.

WDM is considered as one of the best technologies to increase bandwidth over an existing

fiber plant. It enables one to create multiple “virtual fibers” over one physical fiber. It does this

by transmitting different wavelengths (or colors) of light down a fiber. WDM was initially

adopted by long distance carriers only because the spending in amplification, dispersion

compensation and regeneration composed most of the network equipment cost in regional and

national SONET networks but now used widely in access networks as well. WDM became

increasingly popular in metro networks when the local exchange carriers grew their networks.

Other than fiber exhaustion, traffic volume is the major economic factor for deploying WDM

technology in all networks.

The WDM layer is protocol and bit rate independent, which means that it can carry ATM

(Asynchronous Transfer Mode), SONET, and/or IP packets simultaneously. WDM technology

may also be used in Passive Optical Networks (PONs) which are access networks in which the

entire transport, switching and routing happens in optical layer. With the inclusion of recent

3R (reshape, retime, retransmit) devices, internal towards the WDM system, circuits utilizing

only WDM equipment can now be built that may span the country. New performance


2

INTRODUCTION & MOTIVATION

monitoring capabilities happen to be built into these devices so that maintenance and repair of

the link can be done. With WDM as the transmission method, the bandwidth of the existing

fiber plant is maximized. WDM operates in the so-called C-band that corresponds to the low-

loss window of the optical fiber. This is the range where the Erbium-Doped Fiber Amplifier

(EDFA) is operative in all networks.

Additionally, higher fiber cost and situations in which fiber constraints are enforced will lead

to more consideration for WDM than SONET because WDM saves a tremendous amount of

fiber within the optical network. WDM systems could be planned for many channels, however,

pay-as-you-grow strategy can be used and channels added based on demand. The amplifier

distance and overall power budget of the system needs to be calculated for the final quantity

of channels right from the start. We do not require O-E-O switch at every interface and can

travel in photonic layer only. All signal arrives at same time independent of what is on the

other wavelength. One of the main advantage of WDM system is that SONET/SDH can be

carried over WDM. The implication is the fact that, in large network designs, the most

optimized network may not necessarily be a single architecture. One part of the network may

adopt SONET rings while another part implements point-to-point. Usually, the core part of the

network will justify a WDM architecture.

WDM has a goal to carry the same traffic in as few topological structure (e.g., rings) as

possible. It does this at the expense of allowing some visitors to traverse longer distances by

mean of routing technique and remove the possibilities of adding new fiber cables and

components than it does in SONET. For any simple example, the very best SONET design

may generate a bunch of topologically different rings, while the most economic WDM

transport network may consist of just a single WDM ring. Therefore, there’s two options in the

topological optimization, each of which need to be decided in the SONET design stage that

which could be a better option.

Traditionally Internet traffic runs on IP which rides on ATM and SONET/SDH or IP over SDH

then to an optical layer. The misconception that IP has to rides on ATM/SDH is the fact that

IP traffic is small and needs to be combined with others services for cost-effective delivery.

Unlike this delusion, the concept of IP over WDM supports voice, video and data traffic and

dedicate the remainder to high-speed data traffic. Elimination of layers (SONET/ATM) will

ease the task of network management and will be cost effective. Because the traffic volume

grows, WDM will eventually prevail and become the choice of the network technology.


3


Since the OTN and WDM layers make up generic Layer-1 Transport network, different service

types can coexist and share the same infrastructure transparently without influencing each

other's performance. As an example, the service provider can offer any combination of the

SONET/SDH services, MPLS, Metro Ethernet and storage services all on the same fiber

network. Furthermore, OTN infrastructure enables transport over longer distances with less

regeneration sites by utilizing Forward Error Correction (FEC) mechanism embedded within

the OTN layer. Thus, the OTN layer forms the most efficient and cost effective Multi Service

Provisioning Platform (MSPP) over WDM infrastructure. The new Optical Transport Network

(OTN) layer evolved over the layer-1 WDM network for enabling more efficient convergence

of traditional SONET/SDH and new data services.

The OTN layer is designed to for highly effective mapping of different protocols and rates into

the same 10G or 100G uplink pipe providing high bandwidth capabilities in simpler transparent

manner at comparatively low cost. The OTN signal incorporates overhead optimized for

efficient direct mapping for LAN, SONET/SDH and SAN signals and other lower rate client

signals over carrier WDM networks. Using the WDM infrastructure in combination with

Optical Transport Network (OTN) layer enables the service providers to map any of the service

offerings to end customer with easy upgrade path over existing fiber network.

At a basic level, OTN defines a frame format that "wraps" data packets, in a format quite

similar to that of a SONET frame. On the other hand, WDM is used to generate signal at

transmitter side by help of LASER, combining the signals, transmitting the signals with

adequate spacing between the channels and then to receive it on receiver end.

ITU-T defines an Optical Transport Network (OTN) as a set of Optical Network Elements

(ONE) connected by optical fiber links, able to provide functionality of transport, multiplexing,

switching, management, supervision and survivability of optical channels carrying client

signals. While using OTN, layer any protocol carried over the network has the same

performance monitoring information, whether it is SONET/SDH, Ethernet or Fibre channel.

The OTN convergence layer is a much less complex technology for transport applications than

SONET/SDH, which is reflected in the much simpler clocking scheme for instance.


4


The requirements of strict synchronization scheme, complex and costly equipment of

SONET/SDH open the doors and motivates for usage of WDM technology for transfer for data.

WDM can be used in access network as an alternate for low cost and high performance.

Basically, we can use CWDM with 16 channels and Dense-WDM with 40 channels both in

replacement of SONET/SDH in access network. But because of the following drawbacks of

using DWDM in access network we prefer to use CWDM.

• Not cost-effective for low channels, low channel recommends CWDM.

• Complicated transmitters and receivers.

• Wide-band channel, CAPEX and OPEX high.

• The frequency domain involved in the network design and management, increase the

difficulty for implementation.

• DWDM requires R-OADM (Reconfigurable OADM) for routing possibilities which is

very complex and expensive to use.

• For access network, DWDM is not cost effective.

• optical loses in filters and other components and harder to diagnose issues.

• And, it depends on amplifiers as it is not easy to produce amplifier that amplifies very

large spectrum area without additional problems or noise.

• DWDM optical systems require a thermoelectric cooler to stabilize the wavelength

emission and absorb the power dissipated by the laser.

• These thermoelectric coolers consume power while adding cost.

• Moe power consumption as compare to CWDM in access network.

The solution of complex and expensive SONET/SDH technology is C-WDM, which is easy to

use, flexible and has 16 available wavelengths in C-band according to ITU-T specifications.

As, in access network we require passive element so it reduces the complexity of the overall

network.

OADM, MUX used with CWDM are no – configurable which is very cheap and easy to use.

It is very easy to setup with targeted future growth path. The cost of network growth is low

incremental as you pay as architecture grow. It’s easy to convert network and upgrade up to 44


5


wavelengths by replacing CWDM with DWDM. CWDM provides reliable, secure and

standard based architecture.

It is simple to install and have a low-cost maintenance. With compact CWDM, we can receive

all the above benefits and much more such as remote monitoring and setup, protection

capabilities and integration with 3rd party networking devices in a cost-effective way, allowing

us to expand as network grow, and utilize the financial as well as physical resources to the

maximum [7]. So, CWDM is an optimum solution for access networks as we discussed above

because of ease of use. For short transmission distances CWDM can reduce terminal costs by

eliminating the temperature control and allowing the emitted wavelengths to drift with ambient

temperature changes.

CWDM stands for Coarse Wavelength Division Multiplexing is the optical transport

technology based on multiplexing of wavelength to wide spacing. It was born with the specific

aim of working in the field of access, aggregate and metropolitan to reduce transport costs,

while they not require high performance in terms of bandwidth, number of channels and

transmission distance [1]. It is efficient and cost effective solution for use both in Linear

Networks (Point-Point, Bus) and Ring topology.

Cost containment of CWDM is derived from the key elements to this technology, which allows

the use of passive optical Oadm and multiplexing/demultiplexing devices which are low cost,

in addition to the absence of optical amplification.

1.1.1 Origin of C-WDM:

Wavelength Division Multiplexing (WDM) transports multiple signals on a single optical fiber

by using different wavelengths to carry each signal. For a given transmission line rate, WDM

multiplies the amount of data that can be carried over the same optical fiber by the number of

wavelengths transported. WDM technologies have been in use since the 1980s, and gained

popularity with carriers after Dense Wavelength Division Multiplexing (DWDM) became

standardized in the mid-1990s.

DWDM enabled carriers to extend the capacity of the SONET/SDH rings in the network core,

without installing new fiber. To cope with increasing bandwidths demands, a new generation

of DWDM systems is being developed today.


6


While DWDM dominates the long-haul network segment, a different WDM technology,

Coarse Wavelength Division Multiplexing (CWDM) is now well-positioned to help carriers

maximize their network capacity in the access, metro and regional network segments. CWDM

supports fewer wavelengths than DWDM, but is available at a fraction of the cost of DWDM

[2]. This makes CWDM attractive for areas with moderate traffic growth projections.

Proprietary CWDM systems have been available since the 1990s, but carriers have been

reluctant to deploy solutions that were not standardized. With full ITU-T standardization

completed in 2003, CWDM deployments will increase dramatically.

Originally, the term "coarse wavelength division multiplexing" was generic, and meant several

different things. In general, these things shared the fact that the choice of channel spacing and

frequency stability was such that erbium doped fiber amplifiers(EDFAs) could not be utilized.

Prior to the relatively recent ITU standardization of the term, one common meaning for coarse

WDM meant two (or possibly more) signals multiplexed onto a single fiber, where one signal

was in the 1550 nm band, and the other in the 1310 nm band [2].

In 2002 the ITU standardized a channel spacing grid for use with CWDM (ITU-T G.694.2),

using the wavelengths from 1270 nm through 1610 nm with a channel spacing of 20 nm.

(G.694.2 was revised in 2003 to shift the actual channel centers by 1nm as shown in table1.1,

so that strictly speaking the center wavelengths are 1271 to 1611nm) Many CWDM

wavelengths below 1470 nm are considered "unusable" on older G.652 specification fibers,

due to the increased attenuation in the 1270–1470 nm bands.

Newer fibers which conform to the G.652.C and G.652.D standards, such as Corning SMF-

28e and Samsung Wide pass nearly eliminate the "water peak" attenuation peak and allow for

full operation of all 18 ITU CWDM channels in metropolitan networks.

The main characteristic of the recent ITU CWDM standard is that the signals are not spaced

appropriately for amplification by EDFAs. This therefore limits the total CWDM optical span

to somewhere near 60 km for a 2.5 Gbit/s signal, which is suitable for use in metropolitan

applications.

The relaxed optical frequency stabilization requirements allow the associated costs of CWDM

to approach those of non WDM optical components. CWDM is also being used in cable

television networks, where different wavelengths are used for the downstream and upstream

https://en.wikipedia.org/wiki/Erbium_doped_fiber_amplifier


7


signals. In these systems, the wavelengths used are often widely separated, for example the

downstream signal might be at 1310 nm while the upstream signal is at 1550 nm.

An interesting and relatively recent development relating coarse WDM is the creation of GBIC

and small form factor pluggable (SFP) transceivers utilizing standardized CWDM

wavelengths. GBIC and SFP optics allow for something very close to a seamless upgrade in

even legacy systems that support SFP interfaces [2]. Thus, a legacy switch system can be easily

"converted" to allow wavelength multiplexed transport over a fiber simply by judicious choice

of transceiver wavelengths, combined with an inexpensive passive optical multiplexing device.

Passive CWDM is an implementation of CWDM that uses no electrical power. It separates the

wavelengths using passive optical components such as bandpass filters and prisms [3]. Many

manufacturers are promoting passive CWDM to deploy fiber to the home.

Table 1.1. Wavelength band used in CWDM.

1.1.2 Features of C-WDM:

• 20 nm channel spacing (G.694.2).

• 4, 8, 12 and 16 wavelength applications.

• Unidirectional or Bidirectional (single fibre).

• Applications up to 10 Gbit/s per wavelength.

• G.652.C & D low water peak fibre.

• G.652.A & B conventional fibre also supported for many applications.

https://en.wikipedia.org/wiki/SFP_transceiver


8


• Spectral dependence of attenuation and dispersion considered.

• Cost-effective applications, through a combination of uncooled single mode

lasers.

• relaxed laser wavelength tolerances and wide pass-band filters

• 90 km reach for 2 bidirectional channels at 1.25 Gbit/s on a single fibre

• 55 km reach for 8 wavelengths at 2.5 Gbit/s

• 42 km reach for 6 bidirectional channels at 1.25 Gbit/s on a single

(conventional) fibre.

• 2 km reach for 16 wavelengths at 2.5 Gbit/s using low water peak fibre.

Fig.1.1. Attenuation and dispersion coefficient curve w.r.t. wavelengths.

1.1.3 Access Network:

Access networks provide connectivity to the end-user customers (residential, commercial,

government/public organizations, laboratories, wireless base stations, etc.). These include both

wired (copper and optical), as well as wireless technologies: ADSL, VDSL, GSM, UMTS,

LTE, Wi-Fi, WiMAX, etc. Clear majority of wired access networks in Europe and the US are

over copper (e.g. ADSL), while several Asian countries (United Arab Emirates, South Korea,

Hong Kong, Japan) have high penetration (up to 85% for the UAE) of optical access [4].


9


Fig.1.2. Example of Passive optical access network.

The Optical Line Terminal (OLT) as shown in fig1.3 at the service provider’s central office

(CO) broadcasts data to several Optical Network Terminals (ONTs) at the customer premises

through the passive fibre network. All ONTs receive the same broadcast data, selecting the

appropriate portion corresponding to the end-user it is serving. Fewer fibres/cables in the

central office (and feeder/exchange) are required by access network and more number of

subscribers per fibre can be served. It takes Lower mean time to repair with access network

due to this simple structure of network.

1.2. MOTIVATION:

The basic idea of the thesis is design and validation of the rules for CWDM in access network.

Additionally, to optimize the access network cost usage of optical bypass, bulk attenuator,

cascading is needed. An algorithm is required in order to get the optimized result for any given

traffic matrix of the network in case of worst-case approach and statistical approach. The

cheaper cost of OADM, MUX/DEMUX motivates us to use WDM technology for the

transportation of traffic at physical layer.

In the beginning, SONET/SDH were the standard protocols used to transfer the data and voice

over optical fibers. But the exponential increase in traffic, low performance and speed limits

the usage of these protocols as they have fixed circuits and limited in bandwidth. The complex

working and expensive equipment divert us towards CWDM in access network.


10


1.3. ADVANTAGES & DISADVANTAGES OF CWDM:

CWDM is the cheap and leading technology in transmission over optical fiber. Following are

the advantage and disadvantage of using CWDM in access network.

1.3.1 Advantages:

• The most important advantage of CWDM is low-cost equipment. In addition, another

advantage of CWDM is to reduce network operating costs. Since CWDM devices are

small, low power consumption, easy maintenance and power supply, it can use the

220V AC power. Because of its wavelength is relatively small, so the board back

up to a small amount.

• CWDM devices with eight wavelengths have no special requirements for optical fiber,

G.652, G.653, G.655 fiber can be used, also can make use of existing fiber optic

cable [8]. CWDM systems can significantly improve the optical fiber transmission

capacity and improve the utilization of optical fiber for optical fiber.

• CWDM has good flexibility and scalability. Using CWDM technology can open the

business for the user in one day or several hours, but also with the increasing business

volume, you can insert a new OTU board for capacity expansion. Improve the quality

of service.

• Using CWDM system in the MAN can make it possible to restore the optical layer.

• Optical layer recovery is more economic than the other layer recovery. Considering

to optical layer recovery is independent of the business and rate, then some of its

original structure without protection system (such as Gigabit Ethernet), we can use

CWDM to be protected.

• As the advantages of CWDM technology, the CWDM get more and more applications

in the telecommunications, broadcasting, enterprise network, campus network and

other areas.

• CWDM is a low-cost WDM transmission technology for MAN access layer. In

principle, CWDM use optical multiplexer making different wavelengths light signals

multiplex to a single fiber for transmission, at the receiving end of the link, with an

optical demultiplexer making the mixed signal in the optical fiber decompose into

different wavelengths signal, connected to the appropriate receiving equipment.


11


1.3.2 Disadvantages:

• Compared with DWDM, CWDM is more forgiving, simpler to work with and cost less,

but you have the lower number of waves and bandwidth.

• It takes some good financial and traffic planning to decide which is best for your

requirements. CWDM multiplexer and demultiplexer gives you a cheaper colour

muxing scheme, but with more constraints on distances and so on. In less demanding

situations, CWDM can be used [8].

• As CWDM is not amplified it utilizes larger spectrum area and each channel uses wider

spectrum range. Meaning it can be produced with cheaper components. But tradeoff is

distance and maximum utilization of the spectrum.

•

1.4. APPLICATION:

Adding CWDM in the optical transport is a simple and cost-effective solution for fiber exhaust

relief. New services can be added over a single existing optical fiber, without interrupting

service to existing customers. CWDM transponders take .85, 1.3 and 1.5 - band optical signals

from a variety of sources such as SONET and Ethernet client devices, and convert them to

CWDM wavelengths that are on the ITU grid (the use of CWDM wavelengths is transparent

to the client devices). The converted signals are then optically multiplexed onto the same fiber

core, each service being carried on a separate wavelength. Carriers can add Metro Ethernet

services to their SONET services, and integrate Ethernet and SONET transport onto the same

fiber, thereby enabling convergence of circuit and packet services at the edge. Typically,

optical transmission systems such as SONET use two fiber cores to achieve bidirectional

transmission.

By using different wavelengths for each direction, a CWDM system can transmit and receive

traffic over a single fiber core, thus cutting in half the number of optical fibres that are needed

for a given application [9]. CWDM is the perfect alternative for carriers who are looking to

increase the capacity of their installed optical network without replacing existing equipment

with higher bit rate transmission equipment, and without installing new fibres. By using

CWDM, carriers will not need to retire equipment before its time, or dig up the ground to install

new fiber.


12


Installing new fiber is a costly venture, especially in metropolitan areas, where it impacts roads

and terrestrial traffic. Enterprise LAN and SAN connection CWDM rings and point-to-point

links are well suited for interconnecting geographically dispersed Local Area Networks

(LANs) and Storage Area Networks (SANs). Corporations can benefit from CWDM by

integrating multiple Gigabit Ethernet, 10 Gigabit Ethernet and Fibre Channel links over a

single optical fiber for point-to point applications or for ring applications.

1.5. ORGANIZATION OF THESIS:

Chapter-2 contains two section: in first section, we will discuss about various linear impairment

occurs during the transmission of signal in network as we working with passive elements and

network. Non-linear impairment will not affect the efficiency of the system as we are not using

amplifiers or any other power driven elements in access network. In this section, we will

discuss about the evolution and effect of all kind of linear impairments in the network. In

second section, we will define the rules for optical access network using these impairment

effect. In this section, we will find some rules to optimize the network in terms of cost and

wavelength used.

Chapter-3 contains two section: in first section, will describe the algorithms to optimized the

C-WDM network without optical bypass, which in return force us to use cascade and hence

considerable losses due to cascade at a node. This will provide channel upgrade-ability to the

customer as the unused wavelength of the waveset is reserved for the connection to upgrade

the connection. In second section, we will describe the algorithm with optical bypass and

cascade. In this section, we will discuss a trade-off between optical bypass because, as we

know, optical bypass increases the losses in network. On the other hand, provide a cost

minimization solution to the network.

Chapter 4 is organised as: In first section, we conclude the various method used for

optimization and evaluation of the network with and without optical bypass. In next section,

we will describe the future scope of C-WDM technology in various area of communication

and networking.

**************************


Politecnico di Milano, P.zza L. da Vinci, 32, 20133 Milano, Italy.

13

CHAPTER-2 OPTICAL RULES FOR

CWDM NETWORKS

In this chapter, we discuss about the different network topology used in access network,

different elements of network required to build it and their specifications. We will discuss in

details about the linear impairment occurs due to passive element and their power penalty.

2.1 NETWORK REQUIREMENTS:

2.1.1. Network Topology:

There are several network topologies used in application of C-WDM in passive optical

network. Some of them are discussed as below:

1. Linear Configuration: - In this configuration, network may or may not contains any add/drop

nodes between the terminal sites. Mux and DeMux are used at the terminal sites at the edges.

It can be used for both CWDM and DWDM applications.

Fig.2.1. Linear topology.

2. Ring with Hub Configuration: - Mux and DeMux are same network elements but there is no

express traffic between them. Add/drop nodes are used between the terminal sites to add or

drop the channels. This can also be used for the application of both CWDM and DWDM.

Fig.2.2. Ring with hub topology.



14

Optical Rules for CWDM Networks

2.1.2. Optical Fibre:

Optical fiber is the most advanced technology used for the transmission of the signal with

minimal losses. It can support next generation services. The benefits of using an optical fiber

are its higher bandwidth, longer distances from the central to the subscriber, the more resistance

to electromagnetic interference, increased security, reduced signal degradation. Using Passive

Optical Network(PON) technology, assumes the removal of repeaters and optical amplifiers

and therefore reducing the initial investment, lower power consumption, less space, fewer

points of failure [10]. Optical fiber is a transmission medium commonly used in data networks,

like passive optical networks and others. It is a thin, transparent and flexible glass or plastic,

by which light pulses are sent to represent data to be transmitted. The beam is completely

contained and it spreads inside the fiber at an angle of reflection above the critical angle of

total reflection, according to Snell’s law. Optical fibers are widely used in telecommunications,

since they allow sending large amounts of data at a great distance and having higher

bandwidths than other forms of communication such as copper cables or wireless transmission.

They are the transmission medium par excellence to be immune to electromagnetic interference

and because signals travel along them with less losses. This transmission mode allows the

transport of a multitude of information, used for applications such as broadband Internet,

telephone and cable television, through more effective signals than copper wires.

Optical fiber mainly contains three layer which are explained in details below:

Fig.2.3. Geometry of Optical fiber

Core: The core is the innermost part of the fiber and is responsible for driving the optical

signals from the source to the receiving device. It is one continuous glass fiber made from high

temperature ultra-pure quartz, plastic or silicon dioxide. Often, the silica glass (SiO2) is usually

doped with materials such as phosphorus oxide (P2O5), germanium oxide (GeO2) or boron



15


oxide (B2O3) to adjust its refractive index. It has a very small diameter, ranging between 10

to 300 mm. The higher is the core diameter the greater the amount of light the cable can carry.

Indeed, the fiber optic cables across the board are classified according to their diameter.

Cladding: It is the middle part of the fiber, which sis mainly used to protect the waves to exit

from the core because this medium has a refractive index lower than the core, so that acts as a

reflective layer which keep the waves trying to escape the nucleus. It is manufactured with

high temperature and made of silicon crystalline nature, and is generally quartz or transparent

plastic. This layer usually adds several layers of plastic to absorb the potential impact or shock

that the fiber can get and provide extra protection against excessive cable bending.

Coating or buffer: The coating is the outer part of the fiber and acts as a shock absorber,

protecting the core and the cladding from damage and external agents. In short, the cable

provides some mechanical protection to manipulation. It is made of plastic material, capable

of protecting the fiber from moisture, crushing, rodents and other environmental hazards. This

part of cable has mainly two sub-layers: the primary sub-layer i.e. buffer and the secondary

sub-layer i.e. coating. This cover can be easily removed by physical or mechanical means to

splicing and gives the fiber a predetermined outer diameter, that can be 125, 250 μm in case of

having only one primary coating and 500 or 900 μm if also have an additional secondary cover.

2.1.3. Oadm/F-Oadm:

An optical add-drop multiplexer (OADM) is a device used in wavelength-division

multiplexing systems for multiplexing and routing different channels of light into or out of

a single mode fibre. This is a type of optical node, which is generally used for the formation

and the construction of optical telecommunications networks [11].

"Add" and "drop" here refer to the capability of the device to add one or more new wavelength

channels to an existing multi-wavelength WDM signal, and/or to drop one or more channels,

passing those signals to another network path. It can be 1x2 or 1x4 channel OADM and can be

either fixed or re-configurable.

Isolation capability of Oadm is no more than 30 dB where add/drop losses varies between 1.3

to 1.9 dB as they are wavelength dependent while the express losses are independent of the

wavelength and is 1.3dB always. In access network, as network coverage area is limited to tens

of kilometre, fixed Oadm are recommended as we have limited wavelength as well.

https://en.wikipedia.org/wiki/Wavelength-division_multiplexing


https://en.wikipedia.org/wiki/Routing

https://en.wikipedia.org/wiki/Light

https://en.wikipedia.org/wiki/Telecommunications



16


If a wavelength is dropped at Oadm drop port and then re-inserted into the same Oadm module,

then, crosstalk affects should be considered as they can reduce the quality of the signal

effectively. The crosstalk influence in passive element is considered up to the next node. No

longer affect is found or we can neglect if we are inserting the same wavelength several times

in the network.

fig.2.4. 1X2 channel OADM in both east and west direction.

The scalability challenge of the Optical-Electrical-Optical architecture was a major reason to

develop alternative technology where much of electronics could be eliminated and which is

easy to maintained and handle. Given that O-E-O architecture is used to convert the traffic

from a WDM compatible signal to a 1310- nm signal only to be immediately converted back

again to a WDM compatible signal, removing the need for converter for the through traffic was

a major reason to invent a new technology which can remove this complex conversion

mechanism.

This gave rise to the Optical Add/Drop Multiplexer (OADM) network element for nodes of

degree two [12]. With an OADM, the traffic remains in the optical domain as it transits the

node, transponders are needed only for the add/drop traffic. The through traffic is said to

optically bypass the node. In typical carrier networks, on average, over 50% of the traffic

entering a node is through traffic; thus, the number of transponders that can be eliminated with

optical bypass is significant.



17


While the OADM itself costs more than two optical terminals, the reduction in transponders

results in an overall lower nodal cost, assuming the level of traffic is high enough.

Channel (acc. To ITU

grid spacing)

lambda(λ) lambda(λ)nm Pin number

47 λ1 1471

49 λ2 1491 D60101-01

51 λ1 1511

53 λ2 1531 D60102-01

55 λ1 1551

57 λ2 1571 D60103-01

59 λ1 1591

61 λ2 1611 D60104-01

Table.2.1. Wavelength specification of 2-channels OADM.

One of the most important properties of an OADM is its degree of reconfigurability. The

earliest commercial OADMs were not configurable. Carriers needed to specify up front which

wavelengths would be added/dropped at a node, with all remaining wavelengths transiting the

node. Once installed, the OADM was fixed in that configuration. Clearly, this rigidity limits

the ability of the network to adapt to changing traffic patterns. Today, however, most OADMs

are configurable.

This implies that any wave-length can be added/dropped at any node, and that the choice of

add/drop wave-lengths can be readily changed without impacting any of the other connections

terminating at or transiting the node. Furthermore, it is highly desirable that the OADM be

remotely configurable through software as opposed to requiring manual intervention. Such

fully configurable OADMs are often called Reconfigurable OADMs, or ROADMs. Table.

Presents the various specs of the OADM given below:



18


Table.2.2. Performance specifications of 1x2 channels OADM pin.

2.1.4. MUX/DEMUX with or without upgrade port:

A multiplexer or mux is a device that selects one of several analog or digital input signals at a

time and forwards the selected input into a single mode optical fiber. A multiplexer of 2n inputs

has n select lines, which are used to select which input line to send to the output. Multiplexers

are mainly used to increase the amount of data that can be sent over the network within a certain

amount of time and bandwidth [3]. A multiplexer is also called a data selector. The basic

multiplexers have several data input lines and a single output line. It also has data- select inputs,

which permit digital data on any one of the inputs to be switched to the output line. It selects

one of several input signals and passes it on to the output.

Fig.2.5. 8-channel Mux/DeMux without upgrade pin.

https://en.wikipedia.org/wiki/Analog_signal

https://en.wikipedia.org/wiki/Digital_signal_(electronics)

https://en.wikipedia.org/wiki/Computer_networks

https://en.wikipedia.org/wiki/Bandwidth_(signal_processing)



19


Fig.2.6. 16-channel Mux/DeMux with upgrade pin.

DEMULTIPLEXER (DEMUX) basically reverses the multiplexing function. It takes data from

one line and distributes them to a given number of output lines. For this reason, the

demultiplexer is also known as a data distributor. A demultiplexer (DEMUX) performs the

reverse operation; it takes a single input and distributes it over several outputs. In other words,

the demultiplexer takes one data input source and selectively distributes it to 1 of N output

channels just like multi-location switch.

Channel (acc. To ITU

grid spacing)

lambda(λ) lambda(λ)nm Pin number

47 λ1 1471

49 λ2 1491

51 λ3 1511

53 λ4 1531 D60105-01

55 λ5 1551

57 λ6 1571

59 λ7 1591

61 λ8 1611

Table.2.3. Wavelength specification of 8-channels Mux/DeMux.



20


It can be used in point-to-point and point-to-multipoint application, and can also work with

wavelength routers. With the application of non-cooling laser technology and EDFA

technology, it has great cost advantage in building broadband MANS and access networks.

It is applicable to the construction of short and medium-distance IP broadband Metropolitan

Area Networks (MANS) and access networks, especially applicable to network carriers who:

1) cannot lay optical cables conveniently;

2) rent optical cables;

3) do not have sufficient optical cables;

4) want to improve the bandwidth utilization of optical cables.

Mux/DeMux used in CWDM passive networks can manage 8 channels or 16 channels with an

upgrade pin mux/DeMux. Each wavelength we used in CWDM has specific mux/DeMux

insertion loss. But our priority is to use the first 8 waves i.e. from 1611nm – 1471nm as they

show less attenuation and insertion loss [3].

2.1.5. Optical Bypass:

Optical bypass is simply a piece of optical fibre cable used to bypass the node if the channel

needs to transmit further more. It is very useful in case we are transmitting from the same

OADM node to different OADM. The disadvantage of using optical bypass is that it increases

the losses in the network and hence degraded the quality of the connection. But by using an

optical bypass we can reduce the cost of network by removing one extra OADM required at

the transmitting node which in addition also reduce the cascade insertion losses.

Fig.2.7. Optical Bypass.

Optical bypass is required mainly in cases where the source or destination nodes of two

connections are same. In this scenario, one of the channel is dropped at the intermediate



21


destination node and the other is passed to next destination by the help of optical bypass. The

main disadvantage of using optical bypass is that while using optical bypass, losses in the

network increased by a factor of as it conquers add and drop both losses for traffic passing

through it. These add/drop losses are wavelength dependent and component dependent so,

varied according to the requirements of component. Hence, affecting the received power for

each connection & number of available wavelengths.

2.1.6. Pluggable Trans-receiver module:

Pluggable are the device which is inserted at transmitter side to color the signal i.e. in

beginning, the signal is Grey at transmitter and no specific wavelength is decided. Then,

pluggable of desired color/wavelength are used into circuit board. The small form-factor

pluggable (SFP) is a compact pluggable transceiver used for both telecommunication and data

communications applications [13]. The form factor and electrical interface are specified by

multi source agreement (MSA) under the auspices of the SFF Committee. It is a popular

industry format jointly developed and supported by many network component vendors.

The SFP interfaces a network device motherboard to fiber or copper networking cable. SFP

transceivers are designed to support SONET, gigabit Ethernet, Fiber Channel, and other

communications standards. Due to its smaller size, SFP obsolesces the formerly ubiquitous

gigabit interface converter (GBIC); the SFP is sometimes referred to as a Mini-GBIC. In fact,

no device with this name has ever been defined in the MSAs.

The SFP+ is an enhanced version of the SFP that supports data rates up to 16 Gbit/s. The SFP+

specification was first published on May 9, 2006, and version 4.1 published on July 6,

2009.SFP+ supports 8Gbit/s Fiber Channel, 10 Gigabit Ethernet and Optical Transport

Network standard OTU-2. It is a popular industry format supported by many network

component vendors.

10 Gbit/s SFP+ modules are the same dimensions as regular SFPs, allowing the equipment

manufacturer to re-use existing physical designs for 24 and 48-port switches and modular line

cards.

Although the SFP+ standard does not include mention of 16G Fiber Channel it can be used at

this speed. Besides the data rate, the big difference between 8G Fiber Channel and 16G Fiber

Channel is the encoding method. 64b/66b encoding used for 16G is a more efficient encoding

mechanism than 8b/10b used for 8G, and allows for the data rate to double without doubling

the line rate. The result is the 14.025 Gbit/s line rate for 16G Fiber Channel.

https://en.wikipedia.org/wiki/Hot-plugging

https://en.wikipedia.org/wiki/Transceiver

https://en.wikipedia.org/wiki/Telecommunication

https://en.wikipedia.org/wiki/Data_communications

https://en.wikipedia.org/wiki/Data_communications

https://en.wikipedia.org/wiki/Form_factor_(design)

https://en.wikipedia.org/wiki/Multi-source_agreement

https://en.wikipedia.org/wiki/Small_Form_Factor_Committee

https://en.wikipedia.org/wiki/Motherboard

https://en.wikipedia.org/wiki/Unshielded_twisted_pair

https://en.wikipedia.org/wiki/SONET

https://en.wikipedia.org/wiki/Gigabit_Ethernet

https://en.wikipedia.org/wiki/Fibre_Channel

https://en.wikipedia.org/wiki/Gigabit_interface_converter

https://en.wikipedia.org/wiki/Data_rate_units

https://en.wikipedia.org/wiki/Fibre_Channel

https://en.wikipedia.org/wiki/10_Gigabit_Ethernet

https://en.wikipedia.org/wiki/Optical_Transport_Network

https://en.wikipedia.org/wiki/Optical_Transport_Network

https://en.wikipedia.org/wiki/64b/66b_encoding

https://en.wikipedia.org/wiki/8b/10b_encoding



22


SFP+ modules can be described as 'limiting' or 'linear' types; this describes the functionality of

the inbuilt electronics [14]. Limiting SFP+ modules include a signal amplifier to re-shape the

(degraded) received signal whereas linear ones do not. Linear modules are mainly used with

the low bandwidth standards which Introduces Direct Attach for connecting two SFP+ ports

without dedicated transceivers.

FP28 module is a 25 Gbit/s interface which has evolved from 100 Gigabit Ethernet, which is

typically implemented with 4 × 25 Gbit/s data lanes. Identical in mechanical dimensions to

SFP and SFP+, SFP28 implements one 28 Gbit/s lane (25 Gbit/s + error correction) for top-of-

rack switch to server connectivity. SFP28 may also be used to "break out" a single 100GbE

port in a top-of-rack switch into four 25 Gbit/s individual server connections. SFP28 functions

with both optical and copper interconnects.

2.1.7. Connectors Identifier:

In the development of fiber optic technology over the last 35 years, many companies and

individuals have invented the "better mousetrap" - a fiber optic connector that was lower loss,

lower cost, easier to terminate or solved some other perceived problem. In all, about 100 fiber

optic connectors have been introduced to the marketplace, but only a few represent most the

market. Here is a rundown of the connectors that have been the leaders of the industry. Most

fiber optic connectors are plugs or so-called male connectors with a protruding ferrule that

holds the fibers and aligns fibers for mating [15]. They use a mating adapter to mate the two

connector ferrules that fits the securing mechanism of the connectors (bayonet, screw-on or

snap-in.) The ferrule design is also useful as it can be used to connect directly to active devices

like LEDs, VCSELs and detectors.

Fig.2.8. Type of Connectors used between fiber cable and components.

https://en.wikipedia.org/wiki/10_Gigabit_Ethernet#SFP.2B_Direct_Attach

https://en.wikipedia.org/wiki/100_Gigabit_Ethernet



23


The big silver connector at the bottom was probably the first commercially successful fiber

optic connector. It was a "pin vise" holding a stripped fiber. The nose piece is spring loaded

and was pushed back when the connector was inserted into a mating adapter. The fiber stuck

out into a drop of index matching fluid on a plastic lens. This solution, yielding about 3 dB

loss.

Above it is the Biconic, the yellow body indicating a single mode version. It was developed by

a team led by Jack Cook at Bell Labs in Murray Hill. The Biconic was molded from a glass-

filled plastic that was almost as hard as ceramic. It started with the fiber being molded into the

ferrule. When single mode versions first appeared, the ferrules were ground to center the fiber

core in the ferrule to reduce loss. Since it was not keyed and could rotate in the mating adapters,

it had an air gap between the ferrules when mated, meaning loss was never less than 0.3 dB

due to Fresnel reflection.

The advent of the ceramic ferrule changed the connector designs forever. The ceramic ferrule

was hard and precise. Fibers were accurately located for alignment and ferrules could be

allowed to touch. Adding in convex ferrules for physical contact between connectors reduced

losses to levels below 0.3 dB for both multi-mode and single-mode varieties.

In the late 90s, small form factor (SFF) connectors became popular, but only the LC (top) has

been a runaway success, both in Telecommunication companies and high bit rate LANs, SANs,

etc. In earliest days of fiber optics, orange, black or grey was multi-mode and yellow single

mode. However, the advent of metallic connectors like the FC and ST made color coding

difficult, so colored boots were often used. The TIA 568 color code for connector bodies and/or

boots is Beige or multi-mode fiber, Blue for single mode fiber, and Green for APC (angled)

connectors.

2.2 OPTICAL RULE FOR DESIGN OF CWDM NETWORK:

CWDM in access network is the replacement of SDH/SONET which are old protocols used

till the date. We need some optical rules for the implementation of CWDM in access network

as there are several limitations of access network & CWDM combining the both. These

limitation force is to design 7 apply so me rule in pre-processing phase of the network to get a



24


cheap and fully functional access network. The main requirements of the optimization rules

are because of the following limitations:

1. Limited number of available wavelength (16 only).

2. More the number of Oadm are used, - higher are the losses as Passive elements are used only. - higher network cost. - complexity of network increases. - coverage area shrink. 3. Variations in path loss w.r.t. wavelength.

4. Few wavelengths cannot have used because of very high attenuation peak(1371-1391nm).

5. Usage of passive element only.

2.2.1 Optical Rule:

Let λ is set of all available wavelengths.

λ = {λ1, λ2, λ3, λ4...λ16}

Where, λ1 > λ2 > λ3 > λ4 ... >λ16

Ai = TX node

Aj = RX node

Where, i, j = {1,2,3,4,5,6,7} and i ≠ j.

Let C is set of all possible connections between node i and node j.

C = {c1 c2 c3 c4...cn}

Where link/span loss of c1 › c2 › c3 ….› cn

and 1,2,3,…,n is connection name.

So, we can say that,

C1 = {Ai1,Aj1} with {K1 }subset of wavelengths.

C2 = {Ai2,Aj2} with {K2} subset of wavelengths.



25


Cn = {Ain,Ajn} with {Kn} subset of wavelengths.

And {K1} {K2} ...{Kn} is a subset or super subset of {λ}

Let Cl is connection from node Ail to Ajl with {Kl}supported wavelengths.

And

Cm is connection between Aim and Ajm with {Km} supported wavelengths.

Where {Kl}, {Km}, {λ} are set of wavelengths.

NOTE: - “{}” shows set of wavelengths.

CASE 1:

IF Cl ∩ Cm ≤ 1

Where, 1 is no. of common node in connection Cl and Cm.

Then,

{Km'} Relates to Cl, Cm Where,{𝐾𝑚′} = {𝐾𝑚} ∩ {𝐾𝑙}

OR

{Kl'} Relates to Cl, Cm Where, {𝐾𝑙′} = {𝐾𝑚} ∩ {𝐾𝑙}

Let us see it with an example and block diagram, explaining the concept of overlapping nodes

and allocation, installation optimization methodology. The idea is to minimize the cost of the

network by minimizing number of Oadm modules, number of wavelengths in access network

which can be achieve by using the explained rules.

Fig2.9. Connection with one common node.



26


Fig2.10. Connection with no common node.

As describe by the rule above, we can assign same set of wavelength to these connections

shown in figure. In figure 2.9, connection A and b share a Oadm module at node 4 hence,

saving wavelength as well as Oadm where, in fig2.10 connection A and C does not share

anything hence, saving the wavelength only. The solution of this case is shown below in figure

2.11& 2.12.

Fig2.11. Installation of Oadm with colour allocation for Case 1.

Fig2.12. Installation of Oadm with colour allocation for Case1.



27


CASE 2:

IF Cl ∩ Cm ≥ 2 Where, 2 is no. of common node in connection Cl and Cm. Then,

CASE2.1:

Check if connection Cl or Cm has a source or destination node in common with each other or

with any other connection. Side by side, check if the connection sharing a source or destination

node should require channel not more than 1 i.e. Nch <= 1. If both the condition is fulfilled,

that pair of connection can be solved with same set of wavelength using an optical bypass at

one of the connection.

{Km'} Relates to Cl, Cm Where,{𝐾𝑚′} = {𝐾𝑚} ∩ {𝐾𝑙}

OR

{Kl'} Relates to Cl, Cm Where, {𝐾𝑙′} = {𝐾𝑚} ∩ {𝐾𝑙}

Let us see this with the help of an example given below in figure 2.13 where two connection

share more than two nodes and can be solved several possible ways.

Fig2.13. Connection with more than one common node.

Fig2.14. Allocation of wavelength with optical bypass.



28


As shown in figure 2.14, an optical bypass is required at node 5 to pass the channel to its

destination node 4. Both Oadm are of same colour considering that connection B and C requires

one channel each. In this way, optimization can be achieved in connections with more than one

node in common.

CASE2.2:

If connection Cl or Cm request more than one channel even they have source/destination node

in common.

OR

If connection Cl or Cm neither have a single node in common nor they are sharing their source

or destination node, then,

{Kl} Relates to Cl, where,{𝐾𝑙} ⊆ {𝜆}

AND

{Km'} Relates to Cm, Where, {𝐾𝑚′} = ({𝐾𝑚} − {𝐾𝑙})

OR

{Km} Relates to Cm, where,{𝐾𝑚} ⊆ {𝜆}

AND

{Kl'} Relates to Cl, where,{𝐾𝑙′} = ({𝐾𝑙} − {𝐾𝑚})

i.e. a new wavelength set is allocated to the connection without depending on number of

requested channel. Let's assume the same example but with more than one channel request by

connection B or C. the solution of the connection is shown below in figure 2.15.

Fig2.15. Installation and allocation of wavelength if channel requested is more than 1. by any of the connection.



29


2.2.2 Optimization of Cost of Network:

Let NCH is no. of channel required in connection between any two nodes.

1. IF NCH ≥ 2,

Then, Adjacent {Km} Relates to Connection 'Cm'.

Cm = Any connection 'm'.

{Km} = subset of wavelengths

i.e. both channel wavelength should be adjacent to each other according to the specifications

of components such as OADM and MUX/DEMUX.

2. IF NCH ‹ 2 & source/destination node are in common between pair of connection,

Then, {Km'} relates to both the connection{𝐾𝑚′} = {𝐾𝑚} ∩ {𝐾𝑙}

Both connection can be solved by using required number of optical bypass (not more than 2

recommended).

Otherwise,

Kln Relates to Connection 'Cl', 𝐾𝑙𝑛 ∈ {𝐾𝑙}, 𝑤ℎ𝑒𝑟𝑒, {𝐾𝑙} ⊆ {𝜆}

Where, Kln is any wavelength from subset {Kl}

and Kmn is any wavelength relates to connection Km.

3. SPECIAL CASE:

Let C0 = Null connection between two nodes.

With NCH = 0 then, bypass that node using an optical bypass.

2.2.3. Finding the No. Of Overlapping/Common Node in Different Connections:

In case of terminal site linear configuration, it is trivial to find out the number of common node

between different pair of connections. In this case, the number of hope travel by each

connection will give us the information of number of common hop/node between them. Some



30


route optimization technique can also be used to confirm the feasibility of each connection in

network.

As we are not using mesh topology, simpler routing technique also can solve the problem. We

can use minimum path length, minimum hop or least used span method to get an optimized

routing.

With ring topology, it is little bit complex to find out he number of common node between the

connections as combining several number of connection can make a closed loop where they

share more than one node but still have the possibility of re usage of wavelength.

Fig.2.16. Access Network for CWDM using passive elements such as OADM

& Mux/DeMux.



31


In above mention network topology, node 1 to 5 are OADM and node 6,7 are hub i.e. Mux and

DeMux as the same network element. WE may use upgrade pin to add additional 8

wavelengths. By considering our network linear i.e. no express traffic between Mux and

DeMux which are the end node/hub nodes, we can find the common node.

Let us take a Traffic matrix to explain the way of choosing number of common node between

different pair of connections. The traffic matrix is given as follows:

Traffic

matrix

Node1 Node2 Node3 Node4 Node5 Node6 Node7

node1 0 0 1 0 1 0 0

node2 0 0 1 1 0 0 0

node3 1 1 0 0 0 0 0

node4 0 1 0 0 1 0 0

node5 1 0 0 1 0 0 0

node6 0 0 0 0 0 0 2

node7 0 0 0 0 0 2 0

Table.2.4. Traffic matrix of a network containing six connections.

Figure 2.16 can be representing linearly by using first and last node as Mux, DeMux and rest

of the node as Oadm. Figure 2.17 represent the linear configuration of above given network.

Fig.2.17. Considering the ring topology as linear network presenting connections.



32


So, in above given example:

• Connection 1,2,3 and 4 which are from node 1 to node 3, node 1 to node 5, node 2 to

node 3 and node 2 to node 4 respectively has more than two common nodes.

• Connection 4 and 5 which are from node 2 to node 4 and from node 4 to node 5

respectively, has exactly 1 node in common

• Connection 6 i.e. from node 6 to node 7 has no node in common with all other networks.

2.3. OPTICAL IMPAIRMENTS & POWER BUDGET:

The optical feasibility of the channels depends on the optical penalties and the power budget

of the system i.e. the link loss allowed by the difference between output power at receiver and

Receiver Sensitivity. In our case, as we are in worst case condition, we are considering average

transmitted power i.e. 0 dBm and at a BER of 10^-4, the power budget become 27dBm.

Optical penalties, i.e. the power margin the design should take to accommodate various kinds

of impairments that either decrease the guaranteed power at RX or reduce the quality of optical

signal. Some of the optical penalties CD and PMD are not managed with power margins (as

already considered in path penalty), but represent a threshold not to exceed. A first estimation

of power budget with penalties must be done before A/D card assignment, because some

possible wavelengths would not be optically feasible. There are various conditions need to be

consider before calculating the optical feasibility of the channel. These are as follows:

1. Power Budget of 27dB with average transmitted power of 0dBm. 2. Attenuation coefficient varies between 0.23 to 0.40(dB/Km) at different wavelength. 3. C.D. is always -200 < C.D. < 1300 (ps/nm). 4. PMD is always PMD < 10 (ps). 5. PDL not more than 0.1dB per Oadm and per span. 6. Isolation = 30dB

7. Insertion loss for Oadm is from 1.4 to 1.9 (varies with wavelength).

8. Insertion loss for Mux/DeMux is from 1.3 to 4.0dB (varies with wavelength).

9. No express traffic between hub.



33


10. Protected path i.e. connection from node-hub is considered to find out maximum length

of network and can be used in case of failure. 11. Cascade loss is equal to the express loss with an extra 0.5dB of interconnection loss. 12. Optical bypass power penalty is calculated in terms of cross-talk penalty.

All the power penalties, thresholds and conditions are describing in details in the next section

where we briefly describe the losses, power penalties and threshold values that should be

known and calculated separately for each connection.

2.4. LOSSES IN ACCESS NETWORK:

The losses in access network can be calculated with worst case approach or statistical approach.

The major difference between both approaches are that in worst case approach we are taking

the minimum transmitted power and maximum path loss which give us results in worst manner

whereas with statistical approach, we are considering the average of transmitted power and

losses with variance of up to three sigma(σ).

In any of the above-mentioned case, while calculating the received power for every connection

in network, we need to consider the losses depend on wavelength, length of link, insertion loss,

etc.

2.4.1. Worst Case Approach:

In this approach, we will consider the minimum transmitted power and maximum losses in the

path and component to find out the feasibility of network in worst scenarios. We can categorise

the losses based on their dependency as follow:

Wavelength dependent loss: The losses which vary according to the selection of wavelength

will be define in this category. They are:

1. Chromatic Dispersion: It is defining as the dispersion of wavelength due to their different

speed of travelling. It can be positive or negative depending on material and waveguide

characteristics. It is a wavelength dependent component which we can calculate for our given

range. It is linear and deterministic in nature. The most familiar example of dispersion is

probably a rainbow, in which dispersion causes the spatial separation of a white light into

components of different wavelengths. However, dispersion also has an effect in many other

circumstances: for example, group velocity dispersion (GVD) causes pulses to spread in optical

fibers, degrading signals over long distances [3].

Chromatic dispersion can be calculated using the formula,

https://en.wikipedia.org/wiki/Rainbow

https://en.wikipedia.org/wiki/Wavelengths

https://en.wikipedia.org/wiki/Optical_fiber




34


𝐶ℎ𝑟𝑜𝑚𝑎𝑡𝑖𝑐𝐷𝑖𝑠𝑝𝑒𝑟𝑠𝑖𝑜𝑛𝐶𝑜𝑒𝑓𝑓.= 𝐷(𝜆) = 𝑆 0 4⁄ [𝜆 − (𝜆0)4 𝜆3⁄ ] ps/(nm.km) equ (1)

where,

D = chromatic dispersion coefficient.

λ = operating wavelength from 1200nm to 1625nm.

λ0=Zero dispersion wavelength which is, 1313 nm.

S0 = zero dispersion slope with a value of 0.086 ps/(nm)^2 km.

Equ (1) will give us C.D. coefficient value which is used to find out chromatic dispersion

value by,

𝐶. 𝐷.= 𝐷(𝜆) ∗ 𝐿𝑒𝑛𝑔𝑡ℎ𝑜𝑓𝑙𝑖𝑛𝑘 ps/nm. Equ (2)

2. Insertion Loss: Loss of signal power resulting from device in an optical fiber are termed

as insertion loss. Mismatch loss are not of our concern as it can have generated if the cable is

not well connected to the device. These are also given in specification of each device we use

and can be added directly to the power penalty. It is different for different component and their

respective path. For example, Oadm has different insertion loss for add/drop and express path,

Mux/DeMux with or without upgrade pin has different insertion loss for different wavelength.

Insertion loss for each component is describe based on component number and wavelength it

satisfies [3]. The total insertion loss in terms of power penalty of the single connection in

network can be calculated as,

𝐼𝑛𝑠𝑒𝑟𝑡𝑖𝑜𝑛𝐿𝑜𝑠𝑠 = 𝐼𝑛𝑠𝑒𝑟𝑡𝑖𝑜𝑛𝐿𝑜𝑠𝑠𝑎𝑡𝑡𝑟𝑎𝑛𝑠𝑚𝑖𝑡𝑡𝑒𝑟 + 𝐼𝑛𝑠𝑒𝑟𝑡𝑖𝑜𝑛𝐿𝑜𝑠𝑠𝑎𝑡𝑟𝑒𝑐𝑒𝑖𝑣𝑒𝑟 + 𝑛

∗ 𝑖𝑛𝑠𝑒𝑟𝑡𝑖𝑜𝑛𝑙𝑜𝑠𝑠𝑎𝑡𝑒𝑥𝑝𝑟𝑒𝑠𝑠𝑛𝑜𝑑𝑒𝑠

where,

Insertion loss at transmitter and receiver depends on the component if it

is a Oadm or Mux/DeMux.

N = number of express nodes between transmitter and receiver.

Insertion loss at express node = loss due to the node between the path of

source and destination node.

3. Attenuation in link: Attenuation in fiber optics, also known as transmission loss, is the

reduction in intensity of the light beam with respect to distance travelled through a transmission

medium. Attenuation coefficients in fiber optics usually use units of dB/km. Due to the

relatively high quality of transparency of modern optical transmission media. The medium is

typically a fiber of silica glass that confines the incident light beam to the inside [3].

Attenuation is an important factor limiting the transmission of a digital signal across large

distances. Attenuation power penalty in optical fiber can be calculated by,

https://en.wikipedia.org/wiki/Fiber_optics



35


𝐴𝑡𝑡𝑒𝑛𝑢𝑎𝑡𝑖𝑜𝑛 = 𝐴 ∗ 𝐿, in dB Equ (3)

Where,

A = Attenuation coefficient in dB/km.

L = length of the link.

Connection Based Losses: These are the losses which depends on property of the connection

and described as:

1. Polarization mode dispersion: Due to imperfections and asymmetries in optical fiber, two

different polarization of light travel with different speed which leads to the dispersion of

polarization mode. It can be due to improper structure of the core of fiber or can be due random

imperfections. It also depends on length of the link. DGD (Differential group delay) can be

calculated based on given PMD parameter value in specification of the devices and optical

fiber [3]. We can take the statistical sum of all the PMD for different spans of network. From

specification of each device we can figure out the power penalties. Can be calculated for each

component and span length. PMD power penalty can be calculated as,

𝑃𝑀𝐷𝑃𝑒𝑛𝑎𝑙𝑡𝑦 = √∑ (𝑃𝑀𝐷𝑖)2𝑛

𝑖=1 + ∑ (𝑃𝑀𝐷𝑗𝑠𝑝𝑎𝑛)2𝑚

𝑗=1 in dB. Equ (4)

where,

𝑃𝑀𝐷𝑗𝑠𝑝𝑎𝑛 = 𝐷𝑝𝑚𝑑 ∗ √𝐿𝑠𝑝𝑎𝑛 Equ (5)

where, Dpmd = PMD parameter of fiber in “𝑝𝑠 √𝑘𝑚⁄ ”.

Lspan = Length of each span in “km”.

PMDi = PMD penalty for each node in connection.

n = no. of nodes in connection

m = no. of span.

2. Polarization dependent losses: It is the ratio of maximum to minimum transmission of an

optical device w.r.t. all state of polarization. It is different for different device and can be notice

in specification of each device. Statistical sum of the PDL of different devices can be taken at

the end. For the path length, PDL carries a very small value(.05dB/100km) which can be

negligible in case of access network as it is limited to 35-40 kilometer [3]. It can be calculated

for each component and fiber cable. The power penalty due to PDL can be calculated by,

𝑃𝐷𝐿𝑃𝑒𝑛𝑎𝑙𝑡𝑦 = 12√∑ (𝑃𝐷𝐿𝑝𝑒𝑛𝑎𝑙𝑡𝑦𝑜𝑓𝑖𝑡ℎ𝑛𝑜𝑑𝑒)2𝑛

𝑖=1 in dB. Equ (6)

Where,

PDL penalty depends on each node in connection.



36


3.Connector Losses: The losses at the point of connection between optical fiber and

components is considered under connector losses. Single mode connectors have losses of 0.1-

0.2 dB per connection [16]. Power Penalty due to Connector loss can be calculated as,

Connector penalty = Penalty due to single connector x no. of connector, in dB.

4. Filter Losses: The losses due to the filtering process at the transmitter and receiver side has

a significant value and are considered under the name of filter loss [16]. Power penalty due to

filter loss can be calculated as,

Filter penalty = filter penalty of single filter x no. of filter, in Db.

5. Ageing Losses: Losses in optical fiber, OADM, MUX/DEMUX increases by the time which

are termed as aging losses. These are component dependent and varies with time. we need to

guarantee our network to work with these aging losses as well. These losses basically tell us

about the end life losses of the specific component [16]. According to specifications of Fiber

Optics Association, we can consider a power penalty of 3 dB due to ageing of the component.

6. Cross Talk Penalty: If two nodes in a network are using same wavelength, then, cross talk

may occur at one of the node. The signal from previous node, which is dropped at a node from

where a new signal is generated, will affect this signal at that add node due to poor isolation

capacity. The cross-talk will be maximum if power from this previous signal is maximum and

power of the new signal is minimum i.e.,

Pinterf = max (Pinterf) and Psignal = min (Psignal)

where,

𝑚𝑎𝑥(𝑃𝑖𝑛𝑡𝑒𝑟𝑓) = 𝑚𝑎𝑥(𝑃𝑖𝑛𝑝𝑢𝑡) − 𝑚𝑖𝑛(𝐼𝑠𝑜𝑙𝑎𝑡𝑖𝑜𝑛) Equ (7)

𝑚𝑎𝑥(𝑃𝑖𝑛𝑝𝑢𝑡) = 𝑚𝑎𝑥(𝑃𝑡𝑥) − 𝑚𝑖𝑛(𝐼𝑛𝑠𝑒𝑡𝑖𝑜𝑛𝐿𝑜𝑠𝑠) − 𝑚𝑖𝑛(𝑠𝑝𝑎𝑛𝑙𝑜𝑠𝑠) Equ (8)

and

𝑚𝑖𝑛(𝑃𝑠𝑖𝑔𝑛𝑎𝑙) = 𝑚𝑖𝑛(𝑃𝑡𝑥) − 𝑚𝑎𝑥(𝑖𝑛𝑠𝑒𝑟𝑡𝑖𝑜𝑛𝐿𝑜𝑠𝑠𝑎𝑡𝑎𝑑𝑑𝑛𝑜𝑑𝑒) Equ (9)

Cross-talk is independent of the eye closure of the output of signal. So, while calculating the

penalty for cross talk the lower level of “1” and upper level of “0” i.e. αo and α1 are kept zero.

So, we can say that,

𝑝𝑒𝑛𝑄(𝜀, 𝛼, 𝛼0) ≃ 𝑝𝑒𝑛𝑄(𝜀, 𝛼1 = 𝛼0 = 0) ≃ 𝑝𝑒𝑛𝑄(𝜀 = 0, 𝛼1, 𝛼0) Equ (10)

where,

ε is cross talk value and α0, α1 is eye closure value.

In case of eye closure, power in these levels are,

P1 = 2*Pave (1- α1) Equ (11)



37


P0 = 2*Pave (1- α0) Equ (12)

But as we know, cross-talk is independent of eye closure levels, Hence, we can take the full

eye opening criteria considering α0 = α1 = 0.

so, P1 = 2* Pave Equ (13)

So, in case of cross-talk power levels are,

𝑃1 = 2 ∗ 𝑃𝑎𝑣𝑒(1 − 𝛼1)[1 − 2 ∗ √𝜀1 − 𝛼1] Equ (14)

𝑃0 = 2 ∗ 𝑃𝑎𝑣𝑒 ∗ 𝛼0[1 − 2 ∗ √𝜀𝛼0] Equ (15)

The lowest level of 1 and 0 can be calculated as,

α0 = α1 = 0

so, 𝑃1 = 2 ∗ 𝑃𝑎𝑣𝑒[1 − 2 ∗ √𝜀] Equ (16)

and

𝑃0 = 0 Equ (17)

Taking the Ratio of equation 13 from equation 16, we will get cross-talk penalty in terms of

power,

which is,

𝑃𝑒𝑛𝑎𝑙𝑡𝑦 = 1 (1 − 2 ∗ √𝜀)⁄ , in dB Equ (18)

7. Optical Bypass Penalty: The power penalty due to insertion of an optical bypass in network

is calculated in terms of cross-talk. Every optical bypass comes with some cross talk between

the transmitted signal and express error signal. So, we can calculate the power penalty of

optical bypass in terms of cross-talk. It is defined as ration between power received through

express path to the power received through optical bypass. This ratio is always content and

hence, independent of wavelength, distance, Oadm modules, the power penalty is always same

as,

𝐶𝑟𝑜𝑠𝑠 − 𝑡𝑎𝑙𝑘 = (𝑃𝑟𝑥 − 𝐼𝑠𝑜𝑙𝑎𝑡𝑖𝑜𝑛) − (𝑃𝑟𝑥 − 𝑎𝑑𝑑𝑙𝑜𝑠𝑠 − 𝑑𝑟𝑜𝑝𝑙𝑜𝑠𝑠) Equ (19)

𝑂𝑝𝑡𝑖𝑐𝑎𝑙 − 𝐵𝑦𝑝𝑎𝑠𝑠𝑃𝑒𝑛𝑎𝑙𝑡𝑦 = 1 (1 − 2 ∗ √(𝐶𝑟𝑜𝑠𝑠 − 𝑡𝑎𝑙𝑘))⁄ Equ (20)

where,

Prx = Received power at drop port of Oadm.

Isolation = Isolation value of Oadm.

Add/Drop Loss = Losses at the add and drop port of optical bypass

8. Cascade Loss: When more than one Oadm module is required at a single node, we need to

consider these extra losses due to the cascading as well. Based on number of channel requested



38


between two nodes, number of connections and required Oadm module, we derive the number

of cascade require at each node. The losses due to cascade is equal to the express loss through

a Oadm with an extra loss of 0.5dB due to interconnection patch cord which is an optical cable

between cascaded Oadm modules. These cascade losses are applied on every connection

passing through these cascaded nodes based on;

- length of each connection i.e. the connection with minimum distance between

source and destination node will be allocated to the outer-most cascaded node. It

means that these connections will bear the losses due to cascade as they have

greater margin than the connection with larger distances.

- Source and destination node of each connection.

The losses can be calculated as,

𝐶𝑎𝑠𝑐𝑎𝑑𝑒𝐿𝑜𝑠𝑠 = 𝐸𝑥𝑝𝑟𝑒𝑠𝑠𝐿𝑜𝑠𝑠𝑎𝑡𝑂𝑎𝑑𝑚 + 𝐼𝑛𝑡𝑒𝑟𝑐𝑜𝑛𝑛𝑒𝑐𝑡𝑖𝑜𝑛𝐿𝑜𝑠𝑠 Equ (21)

Where,

Express Loss can be seen from specifications of Oadm module.

Interconnection loss = 0.5dB

At the end, total losses in terms of power penalty are calculated for both beginning of life and

end of life in uplink and downlink. The difference in power at uplink and downlink are mainly

due to following reasons:

• Connector loss can be varying from 0.1 to 0.2 dB.

• No. of splices in uplink and downlink optical fiber cable can be different and

hence total splice loss varies.

• Attenuation due to cut in a fibre link may affect the total loss.

• Temperature variation may affect the total loss.

Losses for Start of Life = Maximum path penalty + filter penalty + Insertion Loss + Polarization

Dependent Losses + Attenuation + Total connector losses + Cascade loss + optical bypass

penalty.

Losses for End of Life = Maximum path penalty + filter penalty + Insertion Loss + Polarization

Dependent Losses + Attenuation + Total connector losses+ Cascade loss + optical bypass

penalty + Ageing margin.

Where,

Maximum path penalty = 2dB



39


Filter penalty for TX/RX =0.2dB

Single connector loss = 0.2dB

Single Splice loss = 0.1dB

Isolation penalty = 0.3 dB

Ageing Margin = 3dB

SMF28E Specifications are used

Micro - macro bend losses are negligible

BER = 10^-4

2.4.2. Statistical Approach:

With this approach, we are more tolerant to the losses as we are taking the average with

variance of up to three sigmas. So, losses can vary up to the variance of three sigmas and hence

providing more degree of freedom to the values. Similarly, transmitted power and received

power also can specified with their average and variance. In this case, we can guarantee the

received power to be higher than targeted power depending on the percentage of tie we need it

higher i.e. if we say received power should be higher than targeted for 66 % of time than sigma

should be one and for 95-96 % it should be two.

With statistical approach, wavelength dependent losses such as attenuation, Chromatic

Dispersion are still deterministic and provide a reliable value as in worst case. While Insertion

loss i.e. component loss is in deterministic even if we are using similar fixed Oadm, we cannot

guarantee the same losses in each component because of variation in characteristics of each

component and hence need to find out the average and variance of every Oadm module in a

connection individually,

⟨𝐼𝐿⟩ = (𝐼𝐿𝑚𝑎𝑥 + 𝐼𝐿𝑚𝑖𝑛) 2⁄ Equ (22)

𝜎𝑖𝑙 = (𝐼𝐿𝑚𝑎𝑥 − 𝐼𝐿𝑎𝑣𝑔) 3⁄ Equ (23)

Or both the values can be given by vendor for every wavelength specifically. Insertion Loss of

component in add, drop and express path is calculated separately with average and variance

value and later can be added linearly such as,

⟨𝐼𝐿𝑎𝑣𝑔⟩ = ⟨𝐼𝐿1⟩ + ⟨𝐼𝐿2⟩+. . . +⟨𝐼𝐿𝑛⟩ Equ (24)

𝜎𝑖𝑙𝑡𝑜𝑡 = 𝜎𝑖𝑙1 + 𝜎𝑖𝑙2+. . . +𝜎𝑖𝑙𝑛 Equ (25)

Similarly, the average and variance of transmitted power will be,



40


⟨𝑃𝑡𝑥⟩ = (𝑃𝑚𝑎𝑥 + 𝑃𝑚𝑖𝑛) 2⁄ Equ (26)

and

𝜎𝑃𝑡𝑥 = (𝑃𝑚𝑖𝑛 − 𝑃𝑎𝑣𝑔) 3⁄ Equ (27)

Then, average received power and its variance can be calculated as follows,

⟨𝑃𝑟𝑥𝑎𝑣𝑔⟩ = ⟨𝑃𝑡𝑥⟩ − ⟨𝐿𝑜𝑠𝑠𝑎𝑣𝑔⟩ Equ (28)

and

𝜎𝑃𝑟𝑥 = 𝜎𝑃𝑡𝑥 + 𝜎𝐿𝑜𝑠𝑠 Equ (29)

Where total loss average and variance can be calculated as,

<Lossavg> =filter penalty + <ILavg> + Polarization Dependent Losses + Attenuation

+ Total connector losses + Cascade loss + optical bypass penalty. Equ (30)

𝜎𝐿𝑜𝑠𝑠 = 𝜎𝑖𝑙𝑡𝑜𝑡 + 𝜎(𝑜𝑡ℎ𝑒𝑟𝑙𝑜𝑠𝑠𝑒𝑠) Equ (31)

Power penalties due to Chromatic dispersion and Polarization Mode Dispersion can be added

to sensitivity to find out the targeted power at receiver as they are deterministic values, and

hence,

𝑃𝑡𝑎𝑟𝑔𝑒𝑡 = 𝑃𝑠𝑒𝑛𝑠𝑖𝑡𝑖𝑣𝑖𝑡𝑦 + 𝑃𝑜𝑤𝑒𝑟𝑃𝑒𝑛𝑎𝑙𝑡𝑖𝑒𝑠(𝑃𝐷𝐿 + 𝐶𝐷) Equ (32)

Now, depending on the guaranteed power at the receiver side i.e. percentage of time we need

the receiver power higher than targeted power, it should fulfil the following condition from

equation (28), (29) and (32),

⟨𝑃𝑟𝑥𝑎𝑣𝑔⟩ − 𝑁 ∗ 𝜎𝑃𝑟𝑥 ≥ 𝑃𝑡𝑎𝑟𝑔𝑒𝑡 Equ (33)

Where,

N can be 0 i.e. 50 % of the time received power is higher.



41


1 i.e. 66 % of the time received power is greater than target power.

2 i.e. 95.4 % of the time received power is higher than targeted and,

3 i.e. 99.7 5 of the time received power is higher.

Hence, by varying the value of N in the equation (31), we can guarantee the received power at

receiver as per the required probability value for begin of life and end of life.

***********************************

Dipartimento di Elettronica, Informazione e Bioingegneria


42

CHAPTER-3 ALGORITHM FOR OPTIMIZATION

OF NETWORK

In this chapter, we will explain the algorithm used to find optimized solution for given network

with use of cascade node only and with optical bypass and cascade also. Later we will explain

the algorithms with an example and explain the solution find out but the algorithm.

3.1. ALGORITHM FOR OPTIMIZATION OF NETWORK WITHOUT

OPTICAL BYPASS & WITH CHANNEL UPGRADE-ABILITY:

Without using an optical bypass there are several benefits and drawbacks. Few of them are that

without using an optical bypass we can reduces the losses in network, more number of

wavelength are available for the network, and it make the network less complex and easy for

the maintenance purposes. This algorithm provides a channel upgrade-ability to the customer.

In future, the customer can increase the number of channel between two nodes as the unused

wavelength from same wavelength set is remain reserved for that connection. This wavelength

can be used only in case another request of channel is made between those two nodes. This

give an extra edge to the customer to further expand the connection form 1 to n channel without

effecting the other nodes in the network.

On the other hand, using a bypass reduces the number of OADM nodes in network and hence,

reduces the overall cost of network, utilize all the available wavelengths per the specifications

of Oadm modules.

The algorithm shown in fig.3.1 explains the rules followed to optimized the network in terms

of cost and capacity without using an optical bypass. The steps followed by algorithms are

explained as follows:

• Define a network by the help of few connections between node to node and

node to hub or vice-versa.

• Based on number of channel requested between two nodes, number of connections and

Oadm module, we derive the number of cascade require at each node.

• The losses due to cascade is equal to the express loss through a Oadm with an extra loss

of 0.5dB due to interconnection patch cord.



43

Algorithm for Optimization of Network

• These cascade losses are applied on every connection passing through these cascaded

nodes based on;

- length of each connection i.e. the connection with minimum distance between source

and destination node will be allocated to the outer-most cascaded node. It means that

these connections will bear the losses due to cascade as they have greater margin than

the connection with larger distances.


• Define all the wavelength based losses such as chromatic dispersion, Polarization mode

dispersion losses, attenuation, insertion loss etc.

• Define losses due to optical fiber, connectors and splices.

• Consider an extra loss of around 3 dB due to ageing to check the feasibility of network

at the end of life.

• Calculate the power penalties of all kind of losses we are considering in network.

• For every connection in network, calculate the losses in terms of power penalty and

power received at every wavelength for begin of life & end of life.

• Compare the received power with sensitivity of the receiver as shown in fig.3.3 and

fig3.4.

• From the margin between received power and receiver sensitivity we can calculate the

maximum number of cascade possible with each connection at every given wavelength.

• Define a set of wavelength for each connection those satisfies C.D., PMD and receiver

sensitivity.

• Arrange connection according to no. of wavelength each connection is compatible

with i.e. connections with least number of available wavelength should be in priority

and these connections should be solved first by algorithm.

• Define duplex, triplets, quadruplets…and so on, of the connections those have

less than two nodes in common i.e. either one or no node in common with

variable named as ‘cmn_node_set”. There should be some wavelengths in

common between the connections of each set.



44


• If there are no set of connection having less than two nodes in common Assign a set

of wavelength to each connection, as per specification of OADM and requirement of

one or more than one channel. As, we cannot use optical bypass and hence force to use

the cascading of OADMs at nodes of network.

• Cascading of OADM should be done wherever required, we will explain it with later

by the help of an example.

• But, if there are some connections satisfying the condition and are present invariable

“cmn_node_set”, assign the wavelength from same couple of wavelengths to those set

of connections as per required number of channels by every connection.

• In the above-mentioned case, connections which are not in set are solved individually

and cascade is used, if required. Here, the consumption of wavelengths is maximum

as independent of number of channel required, a new set of wavelength is required for

every unsolved connection.

In this way, we can assign the wavelength to several connections using minimum number of

wavelengths and OADM node, hence, reach to optimized solution.



45


Fig.3.1. Algorithm for finding optimized solution by cascaded nodes & without using optical bypass.



46


3.1.1. Network topology with The Output of the MATLAB:

Fig.3.2. A CWDM passive network with seven connections.



47


Fig.3.3 Linear presentation of the network example.

The network contains connection from 2 to 7, two connection from node 6 to node 7, from

node 1 to node 2, from node 1 to node 3, from node 2 to node 6, from node 3 to node 6, from

node 6 to node 7 respectively.

Traffic

matrix 1 2 3 4 5 6 7

1 0 1 1 0 0 0 0

2 1 0 0 0 0 1 1

3 1 0 0 0 0 1 0

4 0 0 0 0 0 0 0

5 0 0 0 0 0 0 0

6 0 1 1 0 0 0 2

7 0 1 0 0 0 2 0

Table.3.1. traffic matrix for seven connection of a network.



48


As given in table 3.1, 0 and 1 are number of channel required between two nodes. 1 to 6 are

total connection. Received power at each connection for all the available 16 wavelengths in

uplink direction is shown below by a plot.

Fig3.4. Received power (in dBm) at each connection for all the available 16 wavelengths in uplink direction.

Fig3.4 & 3.5 represents the output power received at every connection at begin of life and end

of life in the uplink and downlink direction. The power received in uplink may vary from

downlink received power because of the reasons as follows:

• Connector loss can be varied from 0.1 to 0.2 dB in uplink and downlink.

• No. of splicing can be different and hence total splice loss vary.

• Attenuation due to cut in a fibre link may affect the total loss.

• Temperature variation may affect the total loss.



49


Fig3.5. Received power (in dBm) at each connection for all the available 16 wavelengths in downlink direction.

Fig. 3.6. Solution of given network with linear configuration.



50


Fig.3.7. Graph presenting the wavelength used per span of the network.

As we discuss above in algorithm, first, it will calculate the power received at destination node

at begin and end of life. Then, finding the connection set those have less than two nodes in

common. This solution provides the channel upgrade-ability to the customer if required. As,

few wavelengths from the wave-set are still unused and can be used for future channel

allocation as shown in figure3.7 which describe the usage of wavelength per span.

In the above-mentioned example, connection 3, 5 and 7 have less than two nodes in common,

hence, solved by the same set of wavelengths i.e. 1611-1591nm. Connection two is identical

to connection 3 so. Solved by save wave-set. The connections are solved on the basis of

priority, as connection 1 has minimum number of wavelengths available, it is solved in first

loop with connection 4 as they have node 2 in common which allow them to reuse the

wavelength shown in figure3.6. Appendix - A provides the MATLAB output of the given

example without usage of the optical bypass.

At the end, algorithm is providing a solution where minimum number of OADM are requires

with least number of wavelengths used for seven connections. This allow us to grow the

network with more number of connections as we still have several wavelengths available

unused. This solution provides an upgrade ability to the customer which means they can ask

for unused wavelength in future which is reserved in this case.



51


3.2. ALGORITHM FOR OPTIMIZATION OF NETWORK USING

OPTICAL BYPASS & COST OPTIMIZATION WITH CHANNEL

UPGRADE-ABILITY CONSTRAINTS:

In access network, use of optical bypass will increase the losses in connection as it assists add

and drop both at the same node. It approximately doubles the losses at node. But on the other

hand, using an optical pass at the source or destination side between two connections will

reduce the cost of the overall network and utilizes all the set of wavelength available in CWDM.

It gives the more optimized solution than using cascade only. Because in this we will use bypass

with cascade because if connection requires more than two channel will be fulfilled by the help

of cascade of F-OADM in a single node.

As shown in fig.3.8 the flowchart is explaining the working of algorithm with use of an optical

bypass and cascade wherever required. Below are the steps explained followed by the

algorithms in case if optical bypass:

• Define a network by the help of few connection between node to node and node to hub

or vice-versa.

• On the basis of number of channel requested between two nodes, number of

connections and Oadm module, we derive the number of cascade require at each node.

• The losses due to cascade is equal to the express loss through a Oadm with an extra

Loss of 0.5dB due to interconnection patch cord.

• These cascade losses are applied on every connection passing through these cascaded

nodes based on;

- length of each connection i.e. the connection with minimum distance between source

and destination node will be allocated to the outer-most cascaded node. It means that

these connections will bear the losses due to cascade as they have greater margin than

the connection with larger distances.




52


• Define all the wavelength based losses such as chromatic dispersion, Polarization mode

dispersion losses, attenuation, insertion loss etc.

• Based on margin at received power, we also find out the number of optical bypass a

connection can have by calculating the optical bypass power penalty.

• Optical bypass power penalty is calculated in terms of cross-talk penalty.

• The ratio between margin at received power to the power penalty of single optical

bypass give us the number of optical bypass we can insert in the connection.

• Even though we can use number of optical bypass, more than two are not

recommended.

• Calculate losses due to optical fiber, connectors and splices.

• Consider an extra loss of around 3 dB due to ageing losses to check the feasibility of

network at the end of life.

• Calculate the power penalties of all kind of losses we are considering in network.

• For every connection in network, calculate the losses in terms of power penalty and

power received at every wavelength for begin of life & end of life.

• Compare the received power with sensitivity of the receiver as shown in fig.3.7 and in

fig.3.8.

• Define a set of wavelength for each connection those satisfies C.D., PMD and

sensitivity.

• Arrange connection according to no. of wavelength each connection is compatible with

i.e. the connections with least number of wavelength available should be prior in

solving by algorithm.

• Define duplex, triplets, quadruplets…and so on, of the connections those have

exactly one node in common with a variable named as ‘cmn_node_set”. There

should be some wavelengths in common between the connections of each set.

• If no set of connection satisfies the condition of less than two nodes in common then,

find set of connections those need less than two channel and have either source node or

destination node in common. We can have assigned wavelength to both the connections

from same couple of wavelength as per specifications of OADM and MUX/DEMUX.

• But, if fewer sets of connection are available in “cmn_node_set”, then, solve those set

of connection with same set of wavelength as per requirement of channels.

• Within the connection set, check if they share common source or destination node, i.e.

if connection from different connection-set have same source or destination nodes and



53


few wavelength in common, we can solve those set of connection with same

wavelength set.

• For those connections, which are not in “cmn_node_set” i.e. not satisfying the condition

will be solved based on either their source or destination node in common or

individually.

• If connection has a source or destination node in common, in this case, we require

optical bypass hence, we need to check the wavelength availability with optical bypass

as it increases the losses which in returns decreased the received power.

• As we previously know the possible number of optical bypass with every connection,

we will test if number of required optical bypass at that wavelength is higher than, lower

than or equal to number a connection can have.

• If two connections still have some wavelength available after use of optical bypass, we

assigned them a set according to specifications and availability of OADM. Rest of

connection are solved individually and wavelength(s) is assigned from the available

waves per connection.



54


Fig.3.8. Algorithm for finding optimized solution using optical bypass & cascaded nodes.



55


3.2.1. Network Topology with The Output of the MATLAB:

Fig.3.9. A CWDM passive network with six connections.

Considering the same example, we discussed above, we try to find out the optimized solution

in terms of cost with upgrade ability constraints.



56


Traffic

matrix 1 2 3 4 5 6

1 0 1 1 0 0 0

2 1 0 0 0 0 1

3 1 0 0 0 0 1

4 0 0 0 0 0 0

5 0 0 0 0 0 0

6 0 1 1 0 0 0

Table3.2. Traffic matrix for six connection of a network.

As given in table 3.2., 0, 1, and 2 are number of channel required between two nodes.

1 to 6 are total connection.

Fig.3.10. Received power at each connection for all the available 16 wavelengths in uplink direction.



57


Fig.3.11. Received power at each connection for all the available 16 wavelengths in downlink direction.

As explained in algorithm, wavelength suitable for every connection in network are selected

based on received power at begin of life and end of life. Firstly, algorithm will find set of

connections those have exactly one node in common. Secondly, it will have solved the set of

connection those satisfied the condition. Appendix – B presents the MATLAB output of the

above given example where optical bypass are applied and wavelength is allocated in optimized

way.

Connection are arranging on priority basis as shown in figure3.12. Connection 1 has least

number of feasible wavelength, it is solved first with connection 4 as they have node 2 in

common. This et of connection is solved by 1531nm. Connection 2 & 6 share the node 6. On

the other hand, connection 2 has source node in common with connection set {4 1}. Connection

6 has destination node in common with destination node of connection 1 from connection set

{4 1}.

In this way, we are saving more number of Oadm modules and wavelength set. So, connection

set {2 6} is solved by 1511nm of the same wavelength set of {4 1}. Then, connection 3,5 and

7 also have single node in common so, all are solved by same wavelength set 1611- 1591nm.



58


Fig. 3.12. Solution of given network with linear configuration.

Fig.3.13. Graph presenting the wavelength used per span of the network.



59


3.3 USING PROTECTED PATH IN LINEAR TOPOLOGY:

With linear topology, we have seen that frequency reuse is possible but with the cost of cascade

of nodes in case of 4 channel between two nodes. One of the case of this technique is to use

protected path.

In this scheme, we use the protected path between node-hub to provide another pair of channel

to the connection. The drawback of this strategy is that we can use protected path only between

node and hub and can provide up to 4 channels without any cascading. Furthermore, we cannot

apply frequency re-usage because the wavelength once provided to any connection will be

available in whole link of the network. The advantage behind using this technique is that we

can use all the sixteen available wavelengths in the network by the help of eight OADM nodes.

Before applying it, we need to find out the link length and span length supported by various

number of nodes from 1 to eight. Fig.3.14 and 3.15 shows how the span length and link length

decrease as we increase the number of OADM nodes in the network. The use of passive element

does not allow us to use the large number of Oadm module at higher distance. The losses

increase with increase in number of nodes in network which in results does not allow us to go

very far from transmitter as the optical channel is not feasible between source and destination

node i.e. received power is much lower than receiver sensitivity & hence no wavelength

satisfies the path. Span length & hence network length decreases gradually with increase in

number of nodes between hub.

Fig.3.14. Link length with 1,2,3…,8 OADM nodes in network.



60


Fig.3.15. Network length with 1,2,3…,8 OADM nodes in network.

The figure 3.14 shows that the span length of the network can vary from 2 to 46 Km and link

length can vary from 17 Km with eight nodes to 93 Km with just one Oadm node in network.

This shows that with maximum length of 17Km and 8 OADM nodes we can solve a network

with maximum 16 connections and wavelengths simultaneously.

This solution helps us in using the protected path from any node to the hub and replacing

cascading of node. The drawback of this method is that we cannot use the protected path from

node to node as we are still in Terminal Site to Terminal Site topology which does not allow

traffic through MUX and DEMUX and they are opaque to each other.

In the next section, we will discuss about the solution for proper ring where traffic can be

regenerated at MUX electronically and the retransmitted into the network to utilize the

protected path for node to node scenario.



61


Table.1 in Appendix – C shows the traffic matrix generated and MATLAB output for the

protected path link in linear network and the wavelength allocated to them in case of 1,2,3...8

OADM node in the network. In case of 8 Oadm nodes, all the sixteen wavelengths can be used

with a link length of 17 Km. The length of network with all possible connections between hub

and node, allocated wavelength is given in the Table which show the usage of protected path

in network.

Fig.3.16. A CWDM passive network with TS-Node connections only.

Where, 0.1 < y<= 2 Km

and node 2 to 9 are fixed-OADM.

The following example show us the result of a network having 8 OADM node and the

solution to it with proper wavelength allocations. Length per span are assumed equal to find

the maximum length of the network supported in case of variable number of Oadm modules.



62


3.4 USING ALL OADM NETWORK WITH RING TOPOLOGY:

With ring topology, a node in the network can communicate to any other node. The traffic

generated is a closed-loop traffic. Every node is connected to each other by at least two path

i.e. normal and protected. The network can be used locally. In this section, we replace the hub

of network with a fix- OADM node with the help of ring topology. The network is shown

below in fig 3.17.

Fig.3.17. A CWDM passive network with All-Oadm nodes in network.

Fig.3.18. Linear presentation of All Oadm network.



63


3.4.1. Received Power at Uplink & Downlink:

The wavelength supported by network in uplink and downlink are shown below in figure 3.19

& figure 3.20. In this topology, the traffic matrix is of a closed loop traffic and the number of

span in network is exactly equal to number of nodes in the network. The power received

remains dependent on all the variable as in previous cases. The losses in this case are bit lower

than in case of hub as the add/drop losses of Mux/DeMux are higher than Oadm as per the

specifications.

Fig.3.19. Received power in uplink direction.

Fig.3.20. Received power in downlink direction.



64


Fig.3.21. Solution of given network in linear configuration.

As shown in fig.3.18, it shows the linear presentation of the closed loop network. The algorithm

which we explain in section 3.1 and 3.2 fits here as well. Fig. 3.21 shows the output of the

algorithm diagrammatically. As shown in figure, connection 2 and 4 form a perfect loop i.e.

they are using both normal and protected path. Connection 3 and 4 has a source node in

common which allow us the usage of optical bypass. As we discuss earlier in the algorithm,

feasibility of usage of optical bypass is calculated in the pre-processing. The number of optical

bypass we can use in every connection at each given wavelength is calculated based on power

penalty for single optical bypass which is calculated in terms of crosstalk penalty. Even though

we can use several number of optical bypass as per the calculation, more than 2 optical bypass

in a single connection is not preferred.

Fig. 3.22 tells us about the usage of wavelength per span. This will give an idea about the

congestion in each span which will further help us in planning for the correct usage of routing

optimization technique as they have advantages and disadvantages at the same time. In the

given traffic matrix, five connection are solved by the help of two wavelengths set and 4 Oadm

modules on the cost of two optical bypass.

From figure 3.22, we can reveal that 1591nm is still available in span 2,3 and 4 where,

wavelength 1531nm is still available in span 2,3 and 1511nm is available in span 2 only.



65


Wavelength 1611nm is used in all the span hence, cannot reuse anywhere in this network. We

can see the algorithm output in Appendix – D for further understanding of the procedure. In

this way, the algorithm tries to provide an optimized solution where, fewer wavelength cannot

reuse in the spans.

Fig.3.22. Wavelength used per span of the network.

3.5 KEY FEATURES OF ALGORITHM:

• Provide customer oriented solution such as channel upgrade-ability and full cost

minimization.

• Minimize the number of Oadm used for a traffic matrix.

• No iteration required as;

-Optical feasibility for each requested connection is calculated in pre-

processing.

-Optical bypass sustainability is verified for each connection in pre-

processing.

-Cascade sustainability at each node is calculated in pre-processing.



66


-Optical bypass is handle while allocation of wavelength.

• Low processing cost.

• Can handle 1,2,4...n-channel between two nodes.

• Provide upgrade-ability to the customer, if requested.

• Minimize the cost by usage of optical bypass.

• Open to Routing optimization techniques (minimum length is implemented).

• Allocation is done on priority basis i.e. the connection with least number of wavelengths

are solved first.

• Wavelength are allocated in best optimized way and are shared by maximum number

of connections.

• Other routing optimization method such as, least use path, least number of hopes and

other routing optimization algorithms can apply without effecting the core algorithm as

it is independent of these routing improvisations.

• Independent of the topology of the network, can be used with any given topology.

• Can be implemented with worst case and statistical approach individually without any

co-relation with algorithm and comparison can be done between both the approaches.

At the end, these algorithms will provide the optimized solution in several possible ways with

or without routing optimization. Routing optimization are mainly used to remove the

congestion from span(s) and distribute the load in overall network. The optical rules and

algorithms are flexible with these optimization techniques and will provide more optimized

results as we have limited number of wavelength to be utilized.

******************************



67

CHAPTER-4 CONCLUSION & FUTURE SCOPE

This chapter is organised as: In first section, we will discuss the conclusion of thesis by

highlighting the benefits of C-WDM technology, algorithm used for optimization in access

networks. In second section, we will discuss the future scope of this technology for aggregate

and core networks or replacement of CWDM by DWDM.

4.1. CONCLUSION:

Firstly, design and validation of optical rules for CWDM access network is achieved in

replacement of SONET/SDH protocols because of the complexity and cost of these protocols.

The combination of OTN with CWDM provide an edge to the system as different service types

can coexist and share the same infrastructure transparently without influencing each other's

performance. Both statistical and worst case approach is applied to get the results in most

optimized way. In the algorithm, we implement usage of bulk attenuator, replacement of Oadm

with Mux/Demuxer and vice versa.

Secondly, we discuss about the algorithms used for the optimization of the network using the

cascade of Oadm and optical bypass. The optimization techniques were discussed in details by

the help of examples and diagram to give a practical view to the problem and its solution in

both worst case and statistical approach.

The main objective of the thesis was to define set of rules on which a network routing should

work with optimized and valid results. In the first algorithm, we were only considering the case

of cascading of the nodes without optical bypass. This provide a channel upgradeable solution

to the customer. The unused wavelength is kept reserved for the same connection(s) so that can

be used later for further extension of the connection. As optical bypass is not required, this will

give an edge to the losses and margin for each connection is higher than expected. The solution

we found with the algorithm was based on following conditions:

• The number of common node between two connections should not be higher than two.

• There should be some wavelength in common between the connections those have less

than two nodes in common.

CONCLUSION & FUTURE SCOPE



68

• Each connection represents a single channel.

• If cascading required at a node of network, the connection with smaller link length

should be weighted with insertion loss due to cascading.

• Two connection with same source and destination node should allocate wavelength of

the same set according to component specifications.

By using these conditions, we define set of connections with less than two nodes in common

and which are solved with least number of wavelengths and Oadm nodes in the network

providing channel upgrade ability to the customer.

In the second algorithm, we were using optical bypass with cascading of the node which in

returns provide a cost minimized solution of the access network. The loss in network increases

significantly as optical bypass is introduced but more than two optical bypass are not

recommended because of the crosstalk penalty. The solution we found after using optical

bypass is not channel upgradeable but use the minimum number of wavelengths and Oadm

modules.

Some additional condition is implemented on the network which are:

• The number of common node between two connections should be exactly one.

• If two connection have same source or destination node, optical bypass should be used

in order to allocate wavelengths of same set to these connections provided that both

connection requires 1 channel each and satisfies wavelength(s) from the same set.

Till now, the algorithms, results are verified and simulated. It is verified that to get optimized

result for the routing of network these algorithm gives practically feasible results which may

reduce the cost and increase the capacity of network in a significant way. The practical

implementation of these algorithm at system level will be very beneficial for the organization

as they are easy to implement into the system.

4.2. FUTURE SCOPE:

As we discuss in earlier section, CWDM is new to optical access network & hence has a vast

area of implementation. Some of them are as follows:

4.2.1. 1-Channel To N-Channel:

In CWDM system the future work can be planned based on the literature review. We will use

the above explained algorithm for more than two channel by using more than single Oadm at

a node in the network. The algorithm we discussed above are feasible with more than two

channels also.




69

These algorithms are not wavelength limited, i.e. there are no constraints on number of

wavelength we can use with the defined rules, which allow us to use these algorithms and

CWDM for n-channels. We can achieve our goal of n- channel by using Mux/Demuxer, by

using cascading of nodes and optical bypass for a feasible optimized routing of the network or

by usage of active components into the access network.

4..2.2. From Cwdm To Dwdm:

As we said above, the algorithms have not any wavelength constraints, which open the door

of using these rules with DWDM as well. As the name suggest it is a Dense Wavelength

Division Multiplexing which has around 40 channels with a band gap of less than 1nm. In Case,

large number of channel are required, we can replace CWDM with DWDM.

We can implement DWDM in access network with or without active components to fulfil the

channel requirement of network in a valid and optimized way. The network coverage can be

increase by using CWDM with active elements. By considering the effect of non-linear

impairments on overall network we can remove the possibility of using transmitter and receiver

with complex configuration at higher bit rate in DWDM.

4.2.3. From Access To Larger Network:

Furthermore, CWDM can be used with active components such as WSS, Amplifiers which

allow us to use these rules for networks such as aggregate and core in future. Algorithm will

work with further constraints of OSNR to find the available wavelengths. We will consider the

non-liners impairments with the use of active elements in network topology.

As we know, amplifiers are not available for amplification of whole spectrum window and only

higher wavelengths near 1500nm can be amplified. So, with these limited number of available

wavelengths we can implement our rules and algorithms for aggregate network. A higher bit

rate is required in aggregate network to satisfy the overall capacity of the different access

networks.

4.2.4. Lab Activity;

Lab Activity 1: Implementation of rules in laboratory with and without optical bypass:

Abstract: in lab, one can implement the algorithm in real world to verify and to find out the

efficiency of the algorithm. In first activity, the goal is to check the rules for access network




70

with passive elements. Which, later can be verified for the same network and active

components to increase the coverage area of network and to increase the quality of signals at

cost of non-linear impairment. Replacing fixed Oadm module with reconfigurable module can

provide more flexible solution or large number of connection can be solved by using same

algorithms discussed earlier.

Lab Activity 2: Implementation of rules for DWDM and larger networks:

Abstract: In this activity, one can check the efficiency of algorithms for larger network such as

aggregate and core networks using CWDM or DWDM multiplexing techniques. In further

steps, we can implement n- channel scenario in aggregate and core network with active

elements.

4.2.5. Developing Software:

One of the main future scope of this work is the development of a flexible software, to be used

with network tools design system, using these algorithms which in practical will play a

significant role in optimization and validation of network for the organization. One can

simulate and check the algorithm in Graphics User Interface to valid and understand the

algorithm. The main motive behind developing this planning tool is the key features of it such

as we can use it offline, fewer input from customer are required, flexible to all routing

optimization techniques etc.

*************************

Refrences



71

REFERENCES

1. https://en.wikipedia.org/wiki/Wavelength-division_multiplexing.

2. http://files.sistele7.webnode.com/200000387-39a5e3a9e0/WDMFibreoptics.pdf.

3. Fiber-Optic Communications Systems, Third Edition. Govind P. Agrawal Copyright

Ù 2002 John Wiley & Sons, Inc. ISBNs: 0-471-21571-6 (Hardback); 0-471-22114-7

(Electronic).

4. http://whatis.techtarget.com/definition/access-network.

5. http://www.cisco.com/c/en/us/support/docs/optical/synchronous-optical-network-

sonet/16180-sonet-sdh.html (sonet).

6. http:/www.webproforum.com/tektronix/fu (sonet/sdh).

7. http://gaem.tlc.unipr.it/gestione/userfiles/File/Cucinotta/WDM,%20DWDM%20e%20

CWDM.pdf (dwdm ).

8. https://globaljournals.org/GJRE_Volume13/7-Performance-Analysis-and-

Comparison.pdf (ad,disad cwdm).

9. https://www.necam.com/ONSD/Collateral/CWDM_Technology_Applications_and_O

perations_05.29.08.pdf (application).

10. https://en.wikipedia.org/wiki/Optical_fiber.

11. http://www.orc.soton.ac.uk/publications/theses/2580_ca/alegriach3.pdf (oadm).

12. OADM". Optical Network. Retrieved 2006-08-07.

13. https://en.wikipedia.org/wiki/Small_form-factor_pluggable_transceiver.

14. http://networking.wikia.com/wiki/Small_form-factor_pluggable_transceiver\.

15. http://www.thefoa.org/tech/connID.htm.

16. http://www.thefoa.org/tech/lossbudg.htm.


http://files.sistele7.webnode.com/200000387-39a5e3a9e0/WDMFibreoptics.pdf

http://whatis.techtarget.com/definition/access-network

http://www.cisco.com/c/en/us/support/docs/optical/synchronous-optical-network-sonet/16180-sonet-sdh.html

http://www.cisco.com/c/en/us/support/docs/optical/synchronous-optical-network-sonet/16180-sonet-sdh.html

http://www.webproforum.com/tektronix/fu

http://gaem.tlc.unipr.it/gestione/userfiles/File/Cucinotta/WDM,%20DWDM%20e%20CWDM.pdf

http://gaem.tlc.unipr.it/gestione/userfiles/File/Cucinotta/WDM,%20DWDM%20e%20CWDM.pdf

https://globaljournals.org/GJRE_Volume13/7-Performance-Analysis-and-Comparison.pdf

https://globaljournals.org/GJRE_Volume13/7-Performance-Analysis-and-Comparison.pdf

https://www.necam.com/ONSD/Collateral/CWDM_Technology_Applications_and_Operations_05.29.08.pdf

https://www.necam.com/ONSD/Collateral/CWDM_Technology_Applications_and_Operations_05.29.08.pdf


http://www.orc.soton.ac.uk/publications/theses/2580_ca/alegriach3.pdf

http://www.optical-network.com/terminology.php?letter=all&id=8

https://en.wikipedia.org/wiki/Small_form-factor_pluggable_transceiver

http://networking.wikia.com/wiki/Small_form-factor_pluggable_transceiver/

http://www.thefoa.org/tech/connID.htm

Appendix A



72

Appendix A

CONNECTION ARRAY WITH PRIORITY(NO. OF WAVELENGTH SUPPORTED) ARE

1 6 2 3 4 5 7

WAVELENGTH SUPPORTED BY CONNECTION ARE

1551 1531 1511 1491 1471 0 0 0 0 0 0 0 0 0 0 0

1611 1591 1571 1551 1531 1511 1491 1471 1451 1431 1411 1351 1311 1291 1271 0

1611 1591 1571 1551 1531 1511 1491 1471 1451 1431 1411 1351 1331 1311 1291 1271

1611 1591 1571 1551 1531 1511 1491 1471 1451 1431 1411 1351 1331 1311 1291 1271

1611 1591 1571 1551 1531 1511 1491 1471 1451 1431 1411 1351 1331 1311 1291 1271

1611 1591 1571 1551 1531 1511 1491 1471 1451 1431 1411 1351 1331 1311 1291 1271

1611 1591 1571 1551 1531 1511 1491 1471 1451 1431 1411 1351 1331 1311 1291 1271

CONNECTION SET WITH 1 COMMON NODE ARE:-

3 5 7 0 0 0 0

3 4 6 0 0 0 0

2 5 7 0 0 0 0

2 4 6 0 0 0 0

4 1 0 0 0 0 0

2 6 0 0 0 0 0

3 6 0 0 0 0 0

4 6 0 0 0 0 0

7 2 0 0 0 0 0

7 3 0 0 0 0 0

7 5 0 0 0 0 0

THEIR RESPECTIVE SET OF AVAILABLE WAVELENGTHS ARE:-

1611 1591 1571 1551 1531 1511 1491 1471 1451 1431 1411 1351 1331 1311 1291 1271

1611 1591 1571 1551 1531 1511 1491 1471 1451 1431 1411 1351 1311 1291 1271 0

1611 1591 1571 1551 1531 1511 1491 1471 1451 1431 1411 1351 1331 1311 1291 1271

1611 1591 1571 1551 1531 1511 1491 1471 1451 1431 1411 1351 1311 1291 1271 0

Appendix A



73

1551 1531 1511 1491 1471 0 0 0 0 0 0 0 0 0 0 0

1611 1591 1571 1551 1531 1511 1491 1471 1451 1431 1411 1351 1311 1291 1271 0

1611 1591 1571 1551 1531 1511 1491 1471 1451 1431 1411 1351 1311 1291 1271 0

1611 1591 1571 1551 1531 1511 1491 1471 1451 1431 1411 1351 1311 1291 1271 0

1611 1591 1571 1551 1531 1511 1491 1471 1451 1431 1411 1351 1331 1311 1291 1271

1611 1591 1571 1551 1531 1511 1491 1471 1451 1431 1411 1351 1331 1311 1291 1271

1611 1591 1571 1551 1531 1511 1491 1471 1451 1431 1411 1351 1331 1311 1291 1271

CONNECTION "4 1" HAVE LESS THAN TWO NODE IN COMMON,SO CAN ALLOCATE SAME SET OF

WAVELENGTH TO EACH CONNECTION

CONNECTION "4" IS FROM NODE 1 TO NODE 2

CONNECTION "4" REQUIRES 1 CHANNEL

CONNECTION " 4 " IS SOLVED BY " 1531 " WAVELENGTH




CONNECTION "3 5 7" HAVE LESS THAN TWO NODE IN COMMON, SO CAN ALLOCATE SAME SET OF

WAVELENGTH TO EACH CONNECTION











CONNECTION "6" REQUIRES "1" CHANNEL

CONNECTION "6" IS SOLVED BY "1571" WAVELENGTH

Appendix A



74

CONNECTIONS "2" AND "3" ARE FROM NODE 6 TO 7

CONNECTION "2" REQUIRES Nch = 1 CHANNEL

CONNECTION " 3 " IS ALREADY SOLVED BY " 1611 " WAVELENGTH


ALL CONNECTION SOLVED !!

Appendix B



75

Appendix B

CONNECTION ARRAY WITH PRIORITY (NO. OF WAVELENGTH SUPPORTED) ARE

1 6 2 3 4 5 7


1551 1531 1511 1491 1471 0 0 0 0 0 0 0 0 0 0 0

1611 1591 1571 1551 1531 1511 1491 1471 1451 1431 1411 1351 1311 1291 1271 0

1611 1591 1571 1551 1531 1511 1491 1471 1451 1431 1411 1351 1331 1311 1291 1271

1611 1591 1571 1551 1531 1511 1491 1471 1451 1431 1411 1351 1331 1311 1291 1271

1611 1591 1571 1551 1531 1511 1491 1471 1451 1431 1411 1351 1331 1311 1291 1271

1611 1591 1571 1551 1531 1511 1491 1471 1451 1431 1411 1351 1331 1311 1291 1271

1611 1591 1571 1551 1531 1511 1491 1471 1451 1431 1411 1351 1331 1311 1291 1271

CONNECTION SET WITH 1 COMMON NODE ARE: -

3 5 7 0 0 0 0

3 4 6 0 0 0 0

2 5 7 0 0 0 0

2 4 6 0 0 0 0

4 1 0 0 0 0 0

2 6 0 0 0 0 0

3 6 0 0 0 0 0

4 6 0 0 0 0 0

7 2 0 0 0 0 0

7 3 0 0 0 0 0

7 5 0 0 0 0 0

THEIR RESPECTIVE SET OF AVAILABLE WAVELENGTHS ARE: -

1611 1591 1571 1551 1531 1511 1491 1471 1451 1431 1411 1351 1331 1311 1291 1271

1611 1591 1571 1551 1531 1511 1491 1471 1451 1431 1411 1351 1311 1291 1271 0

1611 1591 1571 1551 1531 1511 1491 1471 1451 1431 1411 1351 1331 1311 1291 1271

1611 1591 1571 1551 1531 1511 1491 1471 1451 1431 1411 1351 1311 1291 1271 0

1551 1531 1511 1491 1471 0 0 0 0 0 0 0 0 0 0 0

1611 1591 1571 1551 1531 1511 1491 1471 1451 1431 1411 1351 1311 1291 1271 0

Appendix B



76

1611 1591 1571 1551 1531 1511 1491 1471 1451 1431 1411 1351 1311 1291 1271 0

1611 1591 1571 1551 1531 1511 1491 1471 1451 1431 1411 1351 1311 1291 1271 0

1611 1591 1571 1551 1531 1511 1491 1471 1451 1431 1411 1351 1331 1311 1291 1271

1611 1591 1571 1551 1531 1511 1491 1471 1451 1431 1411 1351 1331 1311 1291 1271

1611 1591 1571 1551 1531 1511 1491 1471 1451 1431 1411 1351 1331 1311 1291 1271

WAVELENGTH ALLOCATION TO THE NETWORK WITH COST OPTIMIZATION IN TERMS OF NUMBER

OF OADM & WITH FLEXIBILITY CONSTRAINTS ARE:

CONNECTIONS “4 1” HAVE EXACTLY ONE NODE IN COMMON, SO CAN ASSIGN SAME SET OF

WAVELENGTH ACC. TO SPECIFICATION OF PASSIVE COMPONENTS


CONNECTION " 4 " REQUIRES " 1 " CHANNEL





TOTAL OADM SAVED BY TWO CONNECTION SET ARE = 4.

TOTAL OADM SAVED BY IDENTICAL CONNECTION & ALREADY SOLVED CONNECTION SET ARE =

1.

TOTAL OADM SAVED BY IDENTICAL CONNECTION & CURRENTLY SOLVING CONNECTION SET ARE

= 3.

CONNECTION SET "4 1" AND "2 6" SHARE "5" NODE AT THE SOURCE OR DESTINATION NODES OF

CONNECTIONS FROM INDIVIDUAL SET.







Appendix B



77

CONNECTIONS “3 5 7" HAVE EXACTLY ONE NODE IN COMMON, SO CAN ASSIGN SAME SET OF

WAVELENGTH










ALL CONNECTIONS ARE SOLVED!!

Appendix C



78

Appendix C

NUMBER OF OADM NODES SOURCE NODE DESTINATION

NODE

ʎ --ALLOCATED

1. 1 2 1611-1591

TOTAL NODE = 3 1 3 1611-1591

LINK LENGTH = 91 Km

2. 1 2 1571-1551

TOTAL NODE = 4 1 3 1611-1591

LINK LENGTH = 62Km 2 4 1571-1551

2 4 1611-1591

3. 1 2 1571-1551

TOTAL NODE = 5 1 3 1611-1591

LINK LENGTH = 57Km 1 4 1531-1511

2 5 1571-1551

3 5 1611-1591

Appendix C



79

4 5 1531-1511

4. 1 2 1571-1551

TOTAL NODE = 6 1 3 1491-1471

LINK LENGTH = 48Km 1 4 1611-1591

1 5 1531-1511

2 6 1571-1551

3 6 1491-1471

4 6 1611-1591

5 6 1531-1511

5. 1 2 1531-1511

TOTAL NODE = 7 1 3 1451-1431

LINK LENGTH = 39Km 1 4 1491-1471

1 5 1611-1591

1 6 1571-1551

Appendix C



80

2 7 1531-1511

3 7 1451-1431

4 7 1491-1471

5 7 1611-1591

6 7 1571-1551

6. 1 2 1531-1511

TOTAL NODE = 8 1 3 1411-1351

LINK LENGTH = 38 Km 1 4 1451-1431

1 5 1491-1471

1 6 1611-1591

1 7 1571-1551

2 8 1531-1511

3 8 1411-1351

4 8 1451-1431

5 8 1491-1471

Appendix C



81

6 8 1611-1591

7 8 1571-1551

7. 1 2 1531-1511

TOTAL NODE = 9 1 3 1331-1311

LINK LENGTH = 26 Km 1 4 1411-1351

1 5 1611-1591

1 6 1491-1471

1 7 1451-1431

1 8 1571-1551

2 9 1531-1511

3 9 1331-1311

4 9 1411-1351

5 9 1611-1591

6 9 1491-1471

7 9 1451-1431

Appendix C



82

8 9 1571-1551

8. 1 2 1531-1511

TOTAL NODE = 10 1 3 1411-1351

LINK LENGTH = 18 Km 1 4 1291-1271

1 5 1451-1431

1 6 1611-1591

1 7 1331-1311

1 8 1491-1471

1 9 1571-1551

2 10 1531-1511

3 10 1411-1351

4 10 1291-1271

5 10 1451-1431

6 10 1611-1591

7 10 1331-1311

Appendix C



83

8 10 1491-1471

9 10 1571-1551

Table.1. Traffic matrix and allocated wavelengths in case of 1,2 or up to 8 OADM nodes.

LENGTH PER SPAN(IN KM) ARE:- 2 2 2 2 2 2 2 2 2


5 12 1 2 3 4 6 7 8 9 10 11 13 14 15 16


1591 1571 1551 1531 1511 1491 1471 1451 1431 1411 1351 1311 1291 1271 0 0

1591 1571 1551 1531 1511 1491 1471 1451 1431 1411 1351 1311 1291 1271 0 0

1611 1591 1571 1551 1531 1511 1491 1471 1451 1431 1411 1351 1331 1311 1291 1271

1611 1591 1571 1551 1531 1511 1491 1471 1451 1431 1411 1351 1331 1311 1291 1271

1611 1591 1571 1551 1531 1511 1491 1471 1451 1431 1411 1351 1331 1311 1291 1271

1611 1591 1571 1551 1531 1511 1491 1471 1451 1431 1411 1351 1331 1311 1291 1271

1611 1591 1571 1551 1531 1511 1491 1471 1451 1431 1411 1351 1331 1311 1291 1271

1611 1591 1571 1551 1531 1511 1491 1471 1451 1431 1411 1351 1331 1311 1291 1271

1611 1591 1571 1551 1531 1511 1491 1471 1451 1431 1411 1351 1331 1311 1291 1271

1611 1591 1571 1551 1531 1511 1491 1471 1451 1431 1411 1351 1331 1311 1291 1271

1611 1591 1571 1551 1531 1511 1491 1471 1451 1431 1411 1351 1331 1311 1291 1271

1611 1591 1571 1551 1531 1511 1491 1471 1451 1431 1411 1351 1331 1311 1291 1271

1611 1591 1571 1551 1531 1511 1491 1471 1451 1431 1411 1351 1331 1311 1291 1271

1611 1591 1571 1551 1531 1511 1491 1471 1451 1431 1411 1351 1331 1311 1291 1271

1611 1591 1571 1551 1531 1511 1491 1471 1451 1431 1411 1351 1331 1311 1291 1271

1611 1591 1571 1551 1531 1511 1491 1471 1451 1431 1411 1351 1331 1311 1291 1271


Appendix C



84

10 5 0 0 0 0 0 0 0 0 0 0 0 0 0 0

8 12 0 0 0 0 0 0 0 0 0 0 0 0 0 0

16 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0

11 2 0 0 0 0 0 0 0 0 0 0 0 0 0 0

15 3 0 0 0 0 0 0 0 0 0 0 0 0 0 0

13 4 0 0 0 0 0 0 0 0 0 0 0 0 0 0

14 6 0 0 0 0 0 0 0 0 0 0 0 0 0 0

9 7 0 0 0 0 0 0 0 0 0 0 0 0 0 0


1591 1571 1551 1531 1511 1491 1471 1451 1431 1411 1351 1311 1291 1271 0 0

1591 1571 1551 1531 1511 1491 1471 1451 1431 1411 1351 1311 1291 1271 0 0

1611 1591 1571 1551 1531 1511 1491 1471 1451 1431 1411 1351 1331 1311 1291 1271

1611 1591 1571 1551 1531 1511 1491 1471 1451 1431 1411 1351 1331 1311 1291 1271

1611 1591 1571 1551 1531 1511 1491 1471 1451 1431 1411 1351 1331 1311 1291 1271

1611 1591 1571 1551 1531 1511 1491 1471 1451 1431 1411 1351 1331 1311 1291 1271

1611 1591 1571 1551 1531 1511 1491 1471 1451 1431 1411 1351 1331 1311 1291 1271

1611 1591 1571 1551 1531 1511 1491 1471 1451 1431 1411 1351 1331 1311 1291 1271

CONNECTIONS "10 5" HAVE EXACTLY ONE NODE IN COMMON, SO CAN ASSIGN SAME SET OF



CONNECTION " 10 " REQUIRES " 2 " CHANNELS

CONNECTION " 10 " IS SOLVED BY " 1571 1551 " SET OF WAVELENGTH






Appendix C



85



























Appendix C



86



























Appendix C



87



ALL CONNECTIONS ARE SOLVED!!

Appendix D



88

Appendix D

3.4.2. Output Of The Algorithm With All Oadm Ring Topology:


1 2 3 4 5


1611 1591 1571 1551 1531 1511 1491 1471 1451 1431 1411 1351 1331 1311 1291 1271

1611 1591 1571 1551 1531 1511 1491 1471 1451 1431 1411 1351 1331 1311 1291 1271

1611 1591 1571 1551 1531 1511 1491 1471 1451 1431 1411 1351 1331 1311 1291 1271

1611 1591 1571 1551 1531 1511 1491 1471 1451 1431 1411 1351 1331 1311 1291 1271

1611 1591 1571 1551 1531 1511 1491 1471 1451 1431 1411 1351 1331 1311 1291 1271


4 2 0 0 0

3 2 0 0 0


1611 1591 1571 1551 1531 1511 1491 1471 1451 1431 1411 1351 1331 1311 1291 1271

1611 1591 1571 1551 1531 1511 1491 1471 1451 1431 1411 1351 1331 1311 1291 127


WAVELENGTH







ALERT: "1" OPTICAL BYPASS REQUIRED !!

OPTICAL BYPASS REQUIRED AT NODE == 1

CONNECTION "1" AND "5" HAS START NODE IN COMMON

CONNECTION "5" IS FROM NODE 3 TO 1 AND REQUIRES Nch = 1 CHANNEL

CONNECTION "5" IS SOLVED BY "1531" SET OF WAVELENGTH


Appendix D



89

CONNECTION "1" IS SOLVED BY "1511" SET OF WAVELENGTH

ALERT: "1" OPTICAL BYPASS REQUIRED!!

OPTICAL BYPASS REQUIRED AT NODE = 2

CONNECTION "3" AND "4" HAS START NODE IN COMMON


CONNECTION "4" IS ALREADY SOLVED BY "1611" SET OF WAVELENGTH


NOW, CONNECTION "3" IS SOLVED BY "1591" SET OF WAVELENGTH

NO MORE CONNECTION AVAILABLE TO SOLVE !!

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