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Prof. Lian K Chen Part 6 - Optical Netwoks 1 IEG 4030 Optical Communications Part VI. Optical Networks Professor Lian K. Chen Department of Information Engineering The Chinese University of Hong Kong [email protected]

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Page 1: IEG 4030 Optical Communications - AMiner · IEG 4030 Optical Communications Part VI. ... • Super-trunk: no fan-out, connection from headend to the hub

Prof. Lian K Chen Part 6 - Optical Netwoks 1

IEG 4030 Optical Communications

Part VI. Optical Networks

Professor Lian K. ChenDepartment of Information EngineeringThe Chinese University of Hong Kong

[email protected]

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Prof. Lian K Chen Part 6 - Optical Netwoks 2

Part VI. Optical Networks• Lightwave System Evolution• Undersea Transmission Systems• Optical Network Hierarchy and Topologies• Subscriber Loop• Passive Optical Networks• CATV systems• LAN/WAN/MAN

– FDDI– SONET/SDH

• All-optical Multiaccess Network• Network Management

– Protection and Restoration in Network Management

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Prof. Lian K Chen Part 6 - Optical Netwoks 3

Lightwave Systems• Traditional Optical Fiber Transmission System

DET EQ DEC

TMGREC

LASERAMP AMP

Opto-Electronic Regenerative Repeater

E|

MUX

E|

DMUX

XMTR RCVRREGRPTR

REGRPTR

Low-RateData Out

Low-RateData In

Traditional Regenerated Transmission Line

E-Mux: electronic multiplexerE-DMUX: elecrtonic demultiplexerXMTR: transmitterREG: regeneratorRPTR: repeaterRCVR: receiverDET: detectorAMP: amplifierEQ: equalizerTMG REC: timing recoveryDEC: decision circuit

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Prof. Lian K Chen Part 6 - Optical Netwoks 4

• Single-channel operation• Opto-Electronic TDM of synchronous data• electronic regenerative repeaters• 30-50km repeater spacing• Distortion and noise do not accumulate• Capacity upgrade requires higher-speed operation

Traditional Optical Fiber Transmission System

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Prof. Lian K Chen Part 6 - Optical Netwoks 5

Optically amplified Fiber Transmission System

• Multi-channel WDM operation• Data-rate and modulation-format transparent• One optical amplifier (per fiber) supports many wavelength channels• 80-140 km amplifier spacing• Distortion and noise accumulate• Graceful growth (upgrade) of channels• Capacity upgrade by adding wavelength-multiplexed channels

OA OAOA

O|

MUX

Data In

XMTRλ1

λN

λ2O

|

DMUX

Data Out

RCVRλ1

λN

λ2XMTR

XMTR

RCVR

RCVR

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Prof. Lian K Chen Part 6 - Optical Netwoks 6

System Limitations• Attenuation → system power budget

– Solutions: optical amplifiers; coherent detection

• Dispersion → pulse broadening → intersymbol interference– Solutions: dispersion compensation - use dispersion-

compensating fibers, dispersion-shifted fibers, pre-chirping; soliton (dispersion and nonlinear effect compensate each other)

• Polarization → polarization dependent gain/loss, polarization mode dispersion (PMD), polarization sensitive → power penalty – Solutions: polarization tracking+polarization controller to fix the

polarization into components, polarization scrambling, polarization diversity, use polarization-maintaining fibers

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Prof. Lian K Chen Part 6 - Optical Netwoks 7

System Limitations• Nonlinear effects → four-wave-mixing (FWM), stimulated Raman

scattering (SRS), stimulated Brilluoin scattering (SBS), self-phase modulation (SPM), cross-phase modulation (XPM) → system degradation– Solutions: advanced modulation format, power control, phase

modulation; frequency assignment

• Noises → reflection noise, phase noise, back-scattering, modal noise, mode partition noise, thermal noise, shot noise, amplifier beat noise, RIN, etc. → power penalty– Solutions: isolator can reduce some types of noises

• All impairments can be remedied by using forward error correction; electronic equalizer can also resolve dispersion problems

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Prof. Lian K Chen Part 6 - Optical Netwoks 8

System Transmission Capacity

Bit

Rat

e -D

ista

nce

( Gb/

skm

)

1970 1975 1980 1985 1990 1995 2000 2005 Year

1101

102

103

104

105

106

107 WHAT’S NEXT ??WDM + Optical AmplifiersOptical AmplifiersCoherent Detection

1.5μm Single-Frequency Laser1.3μm SM Fiber0.8μm MM Fiber

First Generation

Second Generation

Fourth Generation

Third Generation

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Prof. Lian K Chen Part 6 - Optical Netwoks 9

Capacity Toward 25 Tbit/s

• Chromatic Dispersion

• Fiber Nonlinearity

• Polarization Mode Dispersion

• Channel Xtalk

• L-band EDFAs

• Raman Amplifiers

• Novel Modulation Format

• Polarization or bidirectional interleaving

Higher Data Rate Closer ChannelSpacing

Wider Optical Bandwidth

Higher Spectral Efficiency

0.05 Bits/Hz >1 Bits/Hz

• Fiber Nonlinearity

OC-48 OC-768 100 GHz 12.5 GHz

10 nm 300 nm

• Available Components

System Transmission Capacity

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Prof. Lian K Chen Part 6 - Optical Netwoks 10

Undersea Transmission Systems• Design Considerations

– span distance– data rate– repeater/amplifier spacing– fault tolerance, system monitoring/supervision, restoration, repair– reliability in components: aging– cost

• Leading supplier– Tycom (formerly Tyco Submarine System)– KDD Submarine Cable Systems– Alcatel Submarine Networks

http://www.telegeography.com/products/map_cable/index.php

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Prof. Lian K Chen Part 6 - Optical Netwoks 11

Undersea Transmission Systems

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Prof. Lian K Chen Part 6 - Optical Netwoks 12

Undersea Transmission Systems

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Prof. Lian K Chen Part 6 - Optical Netwoks 13

Undersea Transmission Systems

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Prof. Lian K Chen Part 6 - Optical Netwoks 14

Undersea Transmission Systems

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Prof. Lian K Chen Part 6 - Optical Netwoks 15

Undersea Transmission Systems

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Prof. Lian K Chen Part 6 - Optical Netwoks 16

Undersea Transmission Systems

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Prof. Lian K Chen Part 6 - Optical Netwoks 17

Submarine cable systems

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Prof. Lian K Chen Part 6 - Optical Netwoks 18

Transmission Aspects

Optical Networks

Multi-Access

Network Management

Services/Applications

• Dispersion• Power Budget• Non-linearity• Polarization, etc.

• Network Topology• Node Architecture• Multiplexing Scheme• Media Access Protocol

• Data/Voice• Video/Image• Interactive Multimedia• Internet/Web Access

• Fault Management• Configuration Management• Performance Management

Optical Networks

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Prof. Lian K Chen Part 6 - Optical Netwoks 19

Optical Network Hierarchy

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Prof. Lian K Chen

About 50,00 Route Miles Of Fiber Cable

Carrier Optical Networks in US

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Prof. Lian K Chen Part 6 - Optical Netwoks 21

Yanji

The Existing Over-Head Fiber Optic Cables

Beijing

XiAn

Shanghai

Hongkong

Wuhan

To Europe

To Japan

Lanzhou

Hohhot

FLAG

To Southeast Asia

To South Korea

To North Korea

To Russia

YiningUrumqi

Korla

Ruoqiang

Lhasa

Golmud

Yinchuan

XiningYulin

Taiyuan

ZhangjiakouChengde

ShijiazhuangTianjin

Hengshui

Qingdao

Dalian

Dandong

Qiqihaer

MudanjiangHarbin

Baicheng

ChangchunFuxin

Shenyang

Qinhuangdao

JinanLianyungangKaifeng

ZhengzhouLuoyang

Chengdu

Kunming

Gejiu

Pingxiang

HaikouZhanjiang

Xingyi

Guiyang

Chongqing

Nanning

Beihai

FuzhouTaipei

HuzhouHangzhou

NanjingHefeiXinyang

Wuhu

Jiujiang

NanchangJianyang

Xiangfan

Shashi

Huaihua Changsha

Guilin

Hengyang

HuizhouGuangzhou

Shenzhen

The Existing Buried Fiber Optic Cables

Backbone Fiber Routes in China

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Prof. Lian K Chen Part 6 - Optical Netwoks 22

Optical Networks • Network Topologies

RingBus

Tree

Star Mesh Multi-hop

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Prof. Lian K Chen Part 6 - Optical Netwoks 23

Network Types• Network Types

Broadcast and Select Network

Static Wavelength Routing Network

λ1,λ2,λ3

λ1’,λ2',λ3’

λ1’’,λ2'’,λ3’’

λ1’,λ2,λ3’’

λ1’’,λ2’,λ3

λ1,λ2'’,λ3’

Dynamic Wavelength Routing Network

Space Switches

λ1

λ2

λ3

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Prof. Lian K Chen Part 6 - Optical Netwoks 24

Broadcast and Select WDM Networks

Tunable receiver/fixed transmitter

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Prof. Lian K Chen Part 6 - Optical Netwoks 25

DLCRT

O E

Traditional Fiber Feeder (Digital Loop Carrier)

EU

Subscriber Loop• Fiber-In-The-Loop (FITL) /Passive Optical Networks (PON)

ONU

O ERT

O E MUX

E OCO

Fiber To The Curb (Active Star)

EU

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Prof. Lian K Chen Part 6 - Optical Netwoks 26

Subscriber Loop (contd.)

POS: Passive Optical Splitter ONU: Optical Network UnitRT: Remote Terminal CO: Central OfficeEU: End-User

ONU

O ECO

POS

1

N

Fiber To The Curb (Passive Optical Network)

EU

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Prof. Lian K Chen Part 6 - Optical Netwoks 27

Fiber-In-The-Loop (FITL)

Okada, FSAN, 1988.

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Prof. Lian K Chen Part 6 - Optical Netwoks 28

Passive Optical Networks (PON)

Optical Line Terminal

Optical Network Terminal

Optical Network Unit

Network Terminals

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Prof. Lian K Chen Part 6 - Optical Netwoks 29

PON Architecture• At CO:

– Optical Line Terminal (OLT) generates downstream traffic on its own or takes the Sonet signal from a co-located Sonet XC.

– OLT aggregates traffic from multiple customers sites using TDM to ensure no interference.

• At Outside plant, – passive optical splitters are used to split signal 2 to 32 branches using

various topologies• At Customer premises

– PON terminates in Optical network unit (ONU), or a.k.a. Optical network terminations (ONT)

– The ONU converts optical signal to specific types of bandwidth (e.g. 10/100 Mb/s Ethernet, ATM, or T1 voice and data) and passes it on to routers, PBX, switches. ONU also uses laser to send upstream traffic to CO.

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Prof. Lian K Chen Part 6 - Optical Netwoks 30

Evolution of Passive Optical Networks

APON(155Mb/s-622Mb/s)

GPON(1.25Gb/s-2.5Gb/s)

BPON(155Mb/s-1.25Gb/s)

EPON(1.25Gb/s)

Downstream:

1550nm for video, 1490nm for data

Upstream:

1310nm

WDM PON(1.25Gb/s-10Gb/s)

Downstream:

1550nm

Upstream:

1310nm

TDM-PON

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Prof. Lian K Chen Part 6 - Optical Netwoks 31

TDM-PON

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Prof. Lian K Chen Part 6 - Optical Netwoks 32

Upstream: Burst-Mode Transmission

ONU

ONU

ONUOLT

• Each ONU has different propagation distance from the OLT

• At the OLT, the receiver will see packets from ONUs with varying amplitudes and phases, also varying inter-packet time-gaps

• For each packet: • Require fast clock recovery to get the clock

• Require fast peak detector to get the best threshold level

Burst-Mode Receivers

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Prof. Lian K Chen Part 6 - Optical Netwoks 33

Ethernet PON

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Prof. Lian K Chen Part 6 - Optical Netwoks 34

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Prof. Lian K Chen Part 6 - Optical Netwoks 35

Major TDM-PON Technologies Summary

6416 nominal, 32 allowed32Number of split

20km10km20kmSpan

D/S: 1244/2488 U/S: 155/2488

D/S: 1244 U/S: 1244

D/S: 622/1244 U/S: 155/622

Speed (Mbps)

ATM and EthernetEthernetATMProtocol

ITU-T G.984IEEE 802.3ahITU-T G.983Standard

GPONEPONBPONCharacteristics

Ref: G Keiser, FTTX concept and application

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Prof. Lian K Chen Part 6 - Optical Netwoks 36

WDM-PON

Q: what are the pros and cons for WDM-PON, compared to TDM-PON?

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Prof. Lian K Chen Part 6 - Optical Netwoks 37

WDM-PON

• WDM-PON: Wavelength Division Multiplexed Passive Optical Network

• use multiple wavelengths, each serves a certain group of users

• higher capacity, future-proof

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Prof. Lian K Chen Part 6 - Optical Netwoks 38

Hybrid Fiber-Coax (HFC)• To provide new interactive service, cable TV systems are gradually

upgraded to HFC architecture.• Cable modem is used to provide internet access (IEE802.14).• Telephone service can be provided through VoIP.

Fiber NodeCentral

Office Fiber Coax Amplifier

200-1000Homes

Down-link: 50-750MHz, @1.55μmUp-link: 5-40MHz, @1.3μm

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Prof. Lian K Chen Part 6 - Optical Netwoks 39

CATV (Community Antenna TeleVision)

• Headend : distribution source; include programs received from satellite, local TV station, together with in-house production programs.

• Super-trunk : no fan-out, connection from headend to the hub.• HUB : distribution node; requires high carrier-to-noise ratio (CNR)

~52-56 dB.• Subscriber : home users, required CNR ~ 35 dB

Headend Hub Hub

Drop line

subscriber

subscriber

Trunk amplifier

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Prof. Lian K Chen Part 6 - Optical Netwoks 40

Modulation format of CATV system(1) AM-VSB (vestigial side-band) :

• simple modulation scheme• compatible to existing modulation format• requires high CNR limited power budget, unless high-power diode-

pump solid state laser (>20 dBm) with external modulation is used. • NTSC : 6MHz spacing, 4.2MHz VSB bandwidth

(2) FM : • easier to achieve since the required CNR ~16.5 dB.• requires more bandwidth (40MHz spacing, 30MHz bandwidth)• typically used in satellite broadcasting and by some CATV operators.

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Prof. Lian K Chen Part 6 - Optical Netwoks 41

Modulation format of CATV system (contd.)

(3) Digital : – baseband– FSK and PSK - spectral efficiency not as good as baseband (0.5-1.0

bit/s/Hz), but easier channel tuning– QPSK - spectral efficiency (2.0 bit/s/Hz)– required large bit-rate (>100Mbit/s) if uncompressed– compression schemes - JPEG(ISO), MPEG(ISO), H.261(CCITT), …

• Channel multiplexing scheme : SCM (subcarrier multiplexing)

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Prof. Lian K Chen Part 6 - Optical Netwoks 42

Distortion in CATV• Sources of noise or distortion :

– transmitter - relative intensity noise (RIN), clipping noise, intermodulation. (RIN is very sensitive to reflection)

– receiver noise - shot noise, thermal noise, circuit noise, APD noise.

• Performance index :

CNR (carrier-to-noise ratio) per channel ~ 52 dBCSO (composite-second-order distortion) ~ -65 dBcCTB (composite-triple-beat distortion) ~ -65 dBc

dBc: dB respect to carrier

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Prof. Lian K Chen Part 6 - Optical Netwoks 43

CNR calculation

where m : modulation index per channel I dc : d.c. photo currentBW : receiver bandwidth Ft: electronic preamp noise figureR eq: receiver equivalent resistance RIN: laser relative intensity noise

The last term (laser intensity contribution) in the denominator is introduced since the noise becomes non-negligible when I dc is large.

Note that the above CNR is per channel.

2

2

1 ( )2

2 4 /

dc

dc t eq dc

m ICNR

e I BW k T BW F R RIN I BW

⋅=

⋅ ⋅ ⋅ + ⋅ ⋅ ⋅ ⋅ + ⋅ ⋅

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Prof. Lian K Chen Part 6 - Optical Netwoks 44

CNR for analog modulation Ex: Assume a laser with

Pdc= 2mW, m= 0.01, RIN = -150 dB/Hz, BW = 4MHz, Ft= 3, R eq= 75Ω, Ro= 1.0 mA/mW

Baseline (without distribution loss, fan-out, ….) CNR is

Q : How to determine the modulation index?Q : When will shot noise/thermal noise/RIN noise dominate?Q : What are the effects when we change the value of m, loss, BW, RL, or

RIN?

3 2

1503 6 6 3 2 610

1 (0.01 1.0 2 10 )2

2 (1.0 2 10 ) 4 10 4 4 10 3/ 75 10 (1.0 2 10 ) 4 10CNR

e k T

−− −

⋅ ⋅ ×=

⋅ ⋅ ⋅ × ⋅ × + ⋅ ⋅ ⋅ × ⋅ + ⋅ ⋅ × ⋅ ×

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Prof. Lian K Chen Part 6 - Optical Netwoks 45

Broadband Local AccessSeveral approaches• xDSL (digital subscriber line) by Telco (telephone company).

(http://www.adsl.com)dedicated bandwidth (<10Mb/s)

• Cable modem by CATV industry (http://www.cablemodem.com)40Mb/s share bandwidth; low cost; reliability and security issues; need

• FTTx (Fiber-to-the-x)bring fiber close to residential building

• Wirelss - LMDS (local multipoint distribution service) (+ WiFi, WiMax)At 28 GHz with 1.3GHz bandwidth by FCC; fast deployment; inexpensive;

limits by rain-fade; • Powerline (http://en.wikipedia.org/wiki/Power_line_communication)

• Satellitewide-coverage; down link traffic only

Ref: Scientific America Oct. 1999.

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Prof. Lian K Chen Part 6 - Optical Netwoks 46

Internet Users Projection

Optical Fiber Telecommunications V.B

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Prof. Lian K Chen Part 6 - Optical Netwoks 47

LAN/MAN• Various network protocols by IEEE

and others

• 802.11: wireless LAN (WLAN)• 802.12: 100 VG-Any LAN• 802.15: Wireless PAN (WPAN)

• 802.15.1 bluetooth• 802.15.2 UWB• 802.15.4 ZigBee

• 802.16: WiMax• 802.17: Resilient Packet Ring

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Prof. Lian K Chen Part 6 - Optical Netwoks 48

Fiber Distributed Data Interface (FDDI), ANSI X3T9.5

• dual counter-rotating token passing ring, one ring is the protection ring

• data rate: 100Mb/s, clock rate: 125Mb/s• support 1000 physical connections (500

terminals) • support a total fiber path length of 200km

(100km dual ring)• line coding: 4B5B• frame format (packet)• protocol: Timed -Token Rotation Protocol

– Ref: R. Jain, “Performance Analysis of FDDI Token Ring Networks: Effect of Parameters and Guidelines for Setting TTRT”, Computer Communications Review, vol. 20, no. 4, pp. 264-275, 1990.

MAC

B A

MAC

B A

MAC

B A

MAC

BA

MAC

BA

MAC

BA

Outer ring used for data

Inner ring for protection

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Prof. Lian K Chen Part 6 - Optical Netwoks 49

Fault-tolerance in FDDI

In case of a link failure, the dual rings will be automatically configured into a single ring as shown below:

MAC

B A

MAC

B A

MAC

BA

MAC

BA

MAC

BA

MAC

B A

Station Station

To Ring 1 To Ring 2 To Ring 1 To Ring 2

Bypass Switch

Node FailureNo Node Failure

station adjacent to failure loops backfailed station

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Prof. Lian K Chen Part 6 - Optical Netwoks 50

SONET and SDH• Synchronous Optical Network (SONET) ANSI T1.105.06• Synchronous Digital Hierarchy (SDH) ITU-T G.957

• SONET: North America standards, SDH: standards in Europe and Japan

• robust for transporting all types of voice, video and data services

SONET/SDH Signal Rates Rate (in MHz) SONET Frame SDH Frame Physical Signal Capacity

51.84 STS-1 - OC-1 28 DS1 155.52 STS-3 STM-1 OC-3 84 DS1 622.08 STS-12 STM-4 OC-12 336 DS1

2488.32 STS-48 STM-16 OC-48 1344 DS1 9953.28 STS-192 STM-64 OC-192 5376 DS1

STS: Synchronous Transport Signal Level (for SONET)STM: Synchronous Transport Module Level (for SDH)

“SONET: now it's the standard optical network”, IEEE Communication Mag. Vo.40, no.5, 2002.

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SONET and SDH (contd.)• direct synchronous multiplexing: individual tributary signals may be

multiplexed, using Add-Drop Multiplexer (ADM) and Digital Cross-Connect, directly into a higher rate SONET signal without intermediate stages of multiplexing

→ cost-effective, flexible telecommunications networking

• provides flexible signal transportation capabilities, capable oftransporting all existing and future signals

→ can overlay to existing networks

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SONET network spansPath: end-to-end; (path)Line: between transport nodes; (multiplex section)Section: between line regenerators (regenerator section)

SONET TERMINAL

MULTIPLEXER

SONET TERMINAL

MULTIPLEXER

SONET DIGTIAL CROSS_CONNECT

SONET REGENERATOR

SONET REGENERATOR

LINE LINE

SECTION SECTIONSECTION

PATH

TRIBUTARY SIGNALS

TRIBUTARY SIGNALS

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• Frame rate: 8000 frames per second; 125μs per frame• Line rate of STS-1

SONET STS-1 Frame Format

3 rows

6rows

3 columns Path Overhead (1 column)

Sectionoverhead

Lineoverhead

STS-1 Synchronous Payload Envelope (SPE)(87 columns)

STS-1=(90 bytes/row)(9 rows/frame)(8 bits/byte)/(125 s/frame) =51.84 Mb/s

μ

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SONET ring architecture• SONET ring architecture

ADM

ADM

ADM

Digital Cross Connect

Terminal Multiplexer

Dual Ring

Integrated Timing System Clock

Protection Ring

CentralExchange

DS1, E1, etc.

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Key features of WDM Network• Simple Capacity upgrade

System capacity can be increased easily by adding more channels operating on different wavelength sufficient apart from the existing ones.

• Transparency Different modulation formats (analog AM, FM, PCM, … or digital ASK, FSK,

PSK, QAM, …) on different channels. • Wavelength routing

Wavelength is used as the intermediate or final address for routing datagram. Wavelength selective devices such as WGR (wavelength grating router) or AWG (array waveguide grating) can be used as the router.

• Wavelength switchingWavelength-switched networks provide re-configurable network architecture

on optical layer. Key components for implementing these networksinclude optical cross-connect, wavelength converter, wavelength router, and optical add-drop.

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Wavelength Routing Networks• Broadcast-and-select networks are difficult to scale to wide-area

networks – no. of wavelength channel required – passive star couplers exhibit high insertion loss as the no. of ports

increases.• Wavelength routing networks overcome the problems by wavelength

reuse, wavelength conversion, and optical switching.

Station 1

λ1

Station 2

Station 5Station 4Station 3

λ1

λ2

Wavelength reuse

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All-Optical Multiaccess Networks• “All-Optical” Networks

– transparent to multiple signal format and bit rate → facilitates upgrade and compatible with most existing electronics

– reduce number of costly electrical interface (?)– manage the enormous capacity on the information highway– provide direct photonic access, add-drop and routing of broadband full

wavelength chunk of information

• “Multiaccess” Networks (don’t confuse with access network) – efficient network resource sharing among network nodes– need multiplexing, routing and switching– techniques: SCMA, WDMA, TDMA, CDMA and their hybrids

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Design Considerations of Multiaccess Networks

• Design Considerations– architectures/topologies → network capacity and connectivity– multi-access schemes and protocols→ network throughput and delay– node complexity → cost– all-optical processing vs. opto-electronic processing – switching speed → multi-/demultiplexing, switching– channel accessibility → device tunability (Tunable Transmitters-Tunable

Receivers, Fixed Transmitters-Tunable Receivers or Tunable Transmitters-Fixed Receivers)

– timing and synchronization– control signaling → network management– optical technology → dispersion, nonlinear effects, crosstalk, noise, …

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Network Management• Network management is essential to operate and maintain any

networks.• However attractive a technology might be, it can be deployed only if it

can be managed.• The cost of managing a large network typically dominates the cost of

the equipment deployed in the network.• For optical networks, certain factors such as transparency limit the

number of parameters that can be monitored.

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Network Management Function• Configuration Management • Performance Management• Fault Management• Security Management• Accounting Management• + Safety Management (optical power)

Network Management

Performance management

Security management

Configuration management

Accounting management

Fault management

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Network ManagementPerformance Management:• measure and monitor the network performance such as network throughput,

user response times, line utilization, signal quality, etc.• ensure network can perform at acceptable level.• gather data analyse data check for thresholds alarms if below

threshold

Configuration Management:• monitor network and system configuration such as equipment inventory,

topology, connection setup, etc.• effects on network operation of hardware and software can be tackled and

managed.

Accounting Management:• measure network utilization to regulate network usage of users, maximize

fairness of network access• usage validation, billing

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NM database

NM agent

Network Element

NM database

NM agent

Network Element

Management System

Network Management Protocols

Network ManagementFault Management:• fault detection generate alarms, fault isolation• automatically fix/recover network problems (restoration)• keep log of faults

Security Management:• control and monitor access to network resources • prohibits information and resource access without

appropriate authorization

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Network Protection• In a network, each link carry data from different sources to different

destination.• Two ways to protect the traffic

(1) path switching - restoration is handled by the source and destination nodes of each individual stream

(2) line switch - restoration is handled by the nodes at both ends of the failed linkLine switching can be implemented by span protection and line protection

connection x

reroute path

x

(a) normal (b) path switching

(c) line switching-span protection

(c) line switching -line protectionx

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• 1+1• 1:1 (only one fiber is on)• 1:N

splitter switch

(a) 1+1

switch switch

(b) 1:1

Working fiber

Protection fiber(c) 1:N

Protection fiber

switch

switch

switchswitch

switch

switch

•••

Working fiber

Working fiber

Working fiber

Low priority data

switc

h

Different Protection Techniques for Point-to-point Links

switc

h