1

LightPath Networking

2

Light Propagation Light propagates

due to total internal reflection

Light > critical angle will be confined to the core

Light < critical angle will be lost in the cladding

3

Fiber Types

Multi-Mode: supports hundreds paths for light.

Single-Mode: supports a single path for light

4

Multi-Mode 50/62.5um core, 125um clad Atten-MHz/km: 200 MHz/km Atten-dB/km: 3dB @ 850nm MMF has an orange

jacket

Single-Mode 9um core, 125um cladding Atten-dB/km: 0.4/0.3dB

1310nm/1550nm SMF has a yellow jacket

Laser

Laser

M uliti M ode

S ing le M ode

Core

Cross section

Cladding

LE D

Laser

M uliti M ode

S ing le M ode

Core

Cross section

Cladding

CoreCladding

Fiber Types

5

Attenuation Vs. Wavelength

6

Degradation In Fiber Optic Cable

Attenuation Loss of light power as the signal travels

through optical cable Dispersion

Spreading of signal pulses as they travel through optical cable

7

Technologies Available

Transmitters (Light Sources) LED’s - 850/1310nm

Used with MMF up to 250Mb/s Short distances <1 Km

Semiconductor Lasers – 850/1310/1550nm VCSEL’s, Fabry Perot and DFB 1310/1550 can be used with MMF or SMF Short to long distances Low to High data rates (Mb/s to Gb/s)

8

FP and DFB Laser Spectrum

FP laser Emits multiple evenly spaced wavelengths Spectral width = 4nm

DFB laser Tuned cavity to limit output to single oscillation / wavelength Spectral width = 0.1nm

Op

tica

l O

utp

ut

Po

we

r (m

W)

FWHM=4nm

Op

tica

l O

utp

ut

Po

we

r (m

W)

FWHM=0.1nm

Wavelength(nm)

Wavelength(nm)

FP Laser Output DFB Laser Output

A B

9

Which Laser Type is Better?

Fabry Perot Ideal for low cost pt-

pt MMF or SMF Not suitable for

WDM due to +/- 30nm variation

Dispersion is a serious issue at Gb/s rates

Distributed Feed Back Used in wavelength

division multiplexing systems

Less susceptible to dispersion than FP laser

Used for medium and long haul applications

10

Technologies Available

Receivers (Detectors) PIN Photodiodes

Silicon for shorter ’s (eg 850nm) InGaAs for longer ’s (eg 1310/1550nm) Good optical sensitivity

Avalanche Photodiodes (APD’s) Up to 50% more sensitivity than PIN diodes Primarily for extended distances in Gb/s rates Much higher cost than PIN diodes

11

Dispersion - Single-Mode

FP and DFB lasers have finite spectral widths and transmit multiple wavelengths

Different wavelengths travel at different speeds over fiber A pulse of light spreads as it travels through an optical fiber

eventually overlapping the neighboring pulse Narrower sources (e.g DFB vs. FP) yield less dispersion Issue at high rates (>1Ghz) for longer distances (>50Km)

Time

Transmitter Receiver

12

Dispersion - Multi-Mode Fiber

Modal Dispersion The larger the core of the fiber, the

more rays can propagate making the dispersion more noticeable

Dispersion determines the distance a signal can travel on a multi mode fiber

13

Attenuation It is the reduction of light power over the length of the

fiber. It’s mainly caused by scattering. It depends on the transmission frequency. It’s measured in dB/km ( ))(log10 10 inout PPdB

14

Chromatic Dispersion (CD)

Light from lasers consists of a range of wavelengths, each of which travels at a slightly different speed. This results to light pulse spreading over time. It’s measured in psec/nm/km.

The chromatic dispersion effects increase for high rates.

Source www.teraxion.com

15

Transmission Bands

Band Wavelength (nm)

O 1260 – 1360

E 1360 – 1460

S 1460 – 1530

C 1530 – 1565

L 1565 – 1625

U 1625 – 1675

Optical transmission is conducted in wavelength regions, called “bands”.

Commercial DWDM systems typically transmit at the C-band

Mainly because of the Erbium-Doped Fiber Amplifiers (EDFA).

Commercial CWDM systems typically transmit at the S, C and L bands.

ITU-T has defined the wavelength grid for xWDM transmission

G.694.1 recommendation for DWDM transmission, covering S, C and L bands.

G.694.2 recommendation for CWDM transmission, covering O, E, S, C and L bands.

16

Single Mode Fiber Standards I

ITU-T G.652 – standard Single Mode Fiber (SMF) or Non Dispersion Shifted Fiber (NDSF). The most commonly deployed fiber (95% of worldwide deployments).

“Water Peak Region”: it is the wavelength region of approximately 80 nanometers (nm) centered on 1383 nm with high attenuation.

17

Single Mode Fiber Standards II

ITU-T G.652c - Low Water Peak Non Dispersion Shifted Fiber.

18

Single Mode Fiber Standards III

ITU-T G.653 – Dispersion Shifted Fiber (DSF) It shifts the zero dispersion value within the C-band. Channels allocated at the C-band are seriously affected

by noise due to nonlinear effects (Four Wave Mixing).

19

Single Mode Fiber Standards IV

ITU-T G.655 – Non Zero Dispersion Shifted Fiber (NZDSF) Small amount of chromatic dispersion at

C-band: minimization of nonlinear effects Optimized for DWDM transmission (C

and L bands)

20

Single Mode Fiber Standards

ITU-TStandard

Name Typical Attenuation

value (C-band)

Typical CD value (C-band)

Applicability

G.652 standard Single Mode Fiber

0.25dB/km 17 ps/nm-km OK for xWDM

G.652c Low Water Peak SMF

0.25dB/km 17 ps/nm-kmGood for CWDM

G.653 Dispersion-Shifted Fiber

(DSF)

0.25dB/km 0 ps/nm-km Bad for xWDM

G.655 Non-Zero Dispersion-

Shifted Fiber (NZDSF)

0.25dB/km 4.5 ps/nm-km Good for DWDM

21

Wavelengths travel independently Data rate and signal format on each

wavelength is completely independent Designed for SMF fiber

Signal 1

Signal 2

Signal 3MUX

Signal 1

Signal 2

Signal 3

DEMUX

WDMMultiplexed signal

Single-mode Fiber

Signal 4 Signal 4

Multiplexing - WDM

22

Multiplexing - WDMWDM – Wave Division Multiplexing Earliest technology Mux/Demux of two optical wavelengths

(1310nm/1550nm) Wide wavelength spacing means

Low cost, uncooled lasers can be used Low cost, filters can be used

Limited usefulness due to low mux count

23

Multiplexing - DWDM

DWDM – Dense Wave Division Multiplexing Mux/Demux of narrowly spaced wavelengths

400 / 200 / 100 / 50 GHz Channel spacing 3.2 / 1.6 / 0.8 / 0.4 nm wavelength spacing

Up to 160 wavelengths per fiber Narrow spacing = higher cost implementation

More expensive lasers and filters to separate ’s Primarily for Telco backbone – Distance Means to add uncompressed Video signals

to existing fiber

24

Multiplexing - CWDM

CWDM – Coarse Wave Division Multiplexing

Newest technology (ITU Std G.694.2) Based on DWDM but simpler and more robust Wider wavelength spacing (20 nm) Up to 18 wavelengths per fiber Uses un-cooled lasers and simpler filters Significant system cost savings over DWDM DWDM can be used with CWDM to increase

channel count or link budget

25

CWDM Optical Spectrum

20nm spaced wavelengths

26

DWDM vs. CWDM Spectrum

1470 1490 1510 1530 1550 1570 1590 1610

Wavelength

dB

1.6nm Spacing

27

xWDM Technology

Dense WDM

1550 1570 1590 16101470 1490 1510 1530

Coarse WDM

1550

20 nm

0,8 nm

• Fine channel spacing, 0.8 nm typical

• High precision stabilization of Lasers

• High component cost

• Wide channel spacing, 20 nm typical

• Lower precision of Lasers

• Significantly lower component cost

/nm

/nm

28

DWDM Migration

Capacity Expansion

• Each CWDM channel can be utilized with 8 DWDM channels

• Resulting maximum system capacity:

8 x 8 = 64 DWDM channels

• CWDM and DWDM channels can be mixed

• Soft migration path

15501470 1490 1510 1530 1570 1590 1610 /nm

29

DWDM Migration

CWDM to DWDM Channel utilization

CW

DM

8ch DWDM

ch8

:D

WD

MCWDM & DWDM

2,5 Gbps

• 8 channel DWDM system per CWDM channel

• Soft migration path

• Mixing of CWDM and DWDM channels

• No interruption of CWDM channels

ch8

:

ch1

ch2

30

Amplification CWDM vs. DWDM

EDFA: Erbium-doped Fibre Amplifier DWDM is typically used for longer distance transport, because EDFA

amplifiers enable very long spans more cost-effectively than CWDM. Amplifiers typically cost approximately US$ 20k or more

EDFA

80 km 80 km

C-band

L-band

{{

1 EDFA amplifies all wavelengths in the C-band

Requires 1 amplifier per wavelength

Requires 1 amplifier per wavelength

CWDM wavelengths

(DWDM wavelengths)

31

How Much Capacity ?

100Gbps

Duo-binaryWave-locker++1b/s/Hz

16 symbol levels – 4 bits per symbol required.

256 symbol levels – 8 bits per symbol required.

40Gbps

NRZ/CS-RZ/Wave-locker+10G overlay 0.4b/s/Hz

DuobinaryWave-locker+

0.8b/s/Hz

16 symbol levels – 4 bits per symbol

10Gbps

No issueNRZ0.1b/s/Hz

Reduced reachWave-lockerNRZ0.2b/s/Hz

Reduced reachNo ROADMsWave-locker+0.4b/s/Hz

100GHz 50GHz 25GHz

32

Optical Routing - Definitions Optical Routers – Optical IN , Optical OUT Photonic Routers – Optical IN & OUT but

100% photonic path OOO- Optical to Optical to Optical switching

Optical switch fabric OEO- Optical to Electrical to Optical

conversion Electrical switch fabric Regenerative input and outputs

33

Photonic Technologies

MEMS (Micro Electro-Mechanical System)

Liquid Crystal MASS (Micro-Actuation and Sensing

System )

34

MEMS Technology Steer the Mirror Tilted mirrors shunt light in various directions 2D MEMS

Mirrors arrayed on a single level, or plane Off or On state: Either deployed (on), not deployed (off)

3D MEMS Mirrors arrayed on two or more planes, allowing light to

be shaped in a broader range of ways Fast switching speed (ns) Photonic switch is 1:1 IN to OUT (i.e. no broadcast

mode)

35

Liquid Crystal Technology

Gate the light No Moving Parts Slow switch speed Small sizes (32x32) Operation based on polarization:

One polarization component reflects off surfaces Second polarization component transmits

through surface

36

MASS Technology

Steer the fiber Opto-mechanics uses piezoelectric

actuators Same technology as Hard Disk Readers and

Ink Jet Printer Heads Small-scale opt mechanics: no sliding parts Longer switch time (<10msec)

37

OE EOOE EOOE EOOE EOOE EOOE EOOE EOOE EOOE EOOE EOOE EOOE EOOE EOOE EOOE EOOE EO

X

EQEQEQEQEQEQEQEQEQEQEQEQEQEQEQEQ

CPUMonitoringInterface

LocalIndication

FiberInputs

ElectricalInputs

FiberOutputs

ElectricalOutputs

OEO Technology

High BW Electrical

XPNT

38

OEO Routing Optical <> Electrical conversion at inputs/outputs

Provides optical gain (e.g. 23 dB) High BW, rate agnostic electrical switching at core

SD, HD, Analog Video (digitized), RGBHV, DVI Fast switching (<10us) Full broadcast mode

One IN to ANY/Many outputs Build-in EO / OE to interface with coax plant

Save converter costs

39

Regeneration - Optical vs Photonic

Photonic is a lossy device that provide no re-amplification or regeneration Signal coming in at –23dBm leaves at –

25dBm OEO router provides 2R or 3R (re-

amplify, reclock, regenerate) Signals come in at any level to –25dBm Leave at –7dBm (1310nm) or 0dBm (CWDM)

40

Applications - Design Considerations

Types of signals Signal associations Fiber infrastructure Distance/Loss Redundancy Remote Monitoring

41

Types of Signals

SDI

HDSDI

ANALOG

DVB-ASI

RGB

RS232/422/485

GPI/GPO

10/100 ETHERNET

GBE

FIBER CHANNEL

70/140 MHz I/F

L-BAND

CATV

SONET OC3/12

T1/E1

DS3/E3

AES

ANALOG

DOLBY EINTERCOM

OPTICAL

ROUTING

WDM

CWDM

DWDM

VIDEO

AUDIO

CONTROL

DATACOM

RF

TELECOM

MULTI

WAVELENGTH

MULTI

FIBEROR

FacilityLINKFacilityLINK - Fiber Optics Platform - Fiber Optics Platform

SPLITTERS

+

PROTECTION

SWITCHING

42

Design ConsiderationsFault Protection Protection against fiber breaks Important in CWDM and DWDM systems Need 2:1 Auto-changeover function with

“switching intelligence” Measurement of optical power levels on

fiber Ability to set optical thresholds Revert functions to control restoration

43

Remote monitoring is key due to distance issues

Monitor Input signal presence and validity Laser functionality and bias Optical Link status and link errors Pre-emptive Monitoring

Input cable equalization level CRC errors on coax or fiber interface Optical power monitoring

Data logging of all error’d events Error tracking and acknowledgment

Design Considerations

44

Design Examples – Single Link

SDI @ 270Mb/s

HDSDI @ 1.485Gb/s

HD OE

Dispersion

40 Km’s

SDI @ 270Mb/s

HDSDI @ 1.485Gb/sHD EO

SD OE40 Km’s

SD EO

-7dBm @ 1310nm

-23dBm

-32dBm

Loss Budget

-7dBm @ 1310nm

SD HD HD

FP DFB

TX Power (dBm) -7 -7 0

RX Sens (dBm) -32 -23 -23

Available Budget 25 16 23

Distance (Km) 40 40 40

Fiber Loss (0.35dB/km@1310)

14 14 14

Connectors 4 4 4

Connector Loss 1 1 1

Total Loss 15 15 15

Headroom 10 1 8

SD HD HD

FP DFP

FP Line width (nm) 4 4 0.2

Dispersion (ps/nm.km) 2 2 2

Distance (km) 40 40 40

Dispersion (ps) 320 320

16

RX Jitter Tolerance (UI) 0.4 0.4 0.4

RX Jitter Tolerance (ps) 1480 270 270

Headroom (ps) 1160

-50 254

45

Post House Facility Link – New

AES

E to O

O to E

SDI @ 270Mb/s

HDSDI @ 1.485Gb/s

E to O

O to E

Mux + EO

OE+Demux

O to E

E to O

Location #1 Location #2

RS422RS422

2 Km’s

SDI @ 270Mb/s

HDSDI @ 1.485Gb/s

GBE

AES

Gbe

RS422 RS422

Analog Video

Analog Audio

1310

CWDM

M16

CWDM D16

Gbe

O to E

E to O

Demux+OE

EO + Mux

Analog Video

Analog Audio

Mux + EO

OE+Demux

Analog Video

Analog Audio

Demux+OE

EO + Mux

10/100 10/100

Mux +EO

Demux +OE

10/100 Mb/s Ethernet

Demux +OE

Mux + EO

Analog Video

Analog Audio

10/100 Mb/s Ethernet

GBE

46

RF Over fiber optics -Applications Typical Satellite Application With SNMP Monitoring

LB EOLB EO LB OELB OE

LB OELB OE

Satellite Satellite ReceiverReceiver

VerticaVerticall

HorizontaHorizontallLNB LNB

PowerPower

L-Band Downlink (950Mhz – 2250Mhz)

IF OEIF OEC or KuC or Ku

Up ConvUp ConvIF EOIF EO

Video ModVideo Mod

IF Uplink (70/140Mhz)

HPAHPA

LB EOLB EO

Remote SNMP

Monitoring & Control

Satellite Satellite ReceiverReceiver

Satellite Satellite ReceiverReceiver

Satellite Satellite ReceiverReceiver

Satellite Satellite ReceiverReceiver

BPX-RFBPX-RF DA8-RFDA8-RFRouterRouter

Satellite Satellite ReceiverReceiver

Satellite Satellite ReceiverReceiver

DA-RFDA-RF

BPX-RFBPX-RF

Video ModVideo Mod

DA-RFDA-RFBPX-RFBPX-RF

Ethernet Ethernet / SNMP/ SNMP

Ethernet Ethernet / SNMP/ SNMP

Ethernet Ethernet / SNMP/ SNMP

47

Large Video MAN – Fully protected

RSK

Pac TV

RSH

OneWilshire

25 mi

25 mi

KNBC KRCAKVEA

BT

DirectTV

KCBS CNN9 Net

Australia

Intelsat

JapanTelecom

FoxSports

VYVXFiber

KSCI

KTTV

RSE

Fox

NCTC

4 mi

0.5

10.5

10.5

1.5

0.5

0.8

Extra 2.3

2.3 2.92.3

7.3

Ent ..Tonight

KTLA

CBS2.1

1.51.1 1.1

1.1

2.7

E!

0

0.5

6.2

0.7

Globesat

0.75KMEX

7.25

8 mi

5.5 mi

11 mi

13.5 mi

9.8 mi

KABCProspect

8 mi5.5 mi

LA Zoo

TVGaming 7.25 Dodger

Stadium2.5

5.75

7.5

KABCCircle seven

48

Single Fiber Technology

49

4Gbps CWDM Link

SANET, AMREJ – cheapest solution Gigabit Ethernet, Low cost switches as repeaters (Cisco 3550) CWDM

Belgrade Novi Sad Subotica

Cisco 6509 Cisco 3550 Cisco 3550

95km 110km

CWDMMUX/DEMUX

CWDMMUX/DEMUX

HU1GE 802.1q

50

Modular xWDM System

Passive Optical Modules

Options:• 8 channels Mux/Demux• 2 channels Add/Drop• 4 channels Add/Drop

Passive Optical

Active OpticalLine

Interf.

Power2Power1

..

8 ch.Mux

Demux

CWDM ch 1CWDM ch 2CWDM ch 3

CWDM ch 8

..CWDMline

..

2 ch.AddDropMux

ch 1 LineWest

LineEast

ch 2A/DWest

ch 1ch 2

A/DEast

.. 4 ch.AddDropMux

ch 1..

ch 4

LineWest

LineEast

A/DWest

A/DEast

ch 1..

Ch 4..

51

Modular xWDM System

Line Interface Modules

Options:• Standard Line Interface (duplex)• Standard Line Interface (simplex)• Protected Line Interface• Add/Drop Line Interface

Passive Optical

Active OpticalLine

Interf.

Power2Power1

StandardDuplex

InternalLine

InternalLine

StandardSimplex

ProtectedWest

ProtectedEast

InternalWest

InternalEast

ExternalWest

ExternalEast

52

Modular xWDM System

Configurable Channels (CWDM Lambdas)

Wavelength color code

• 1470 nm

• 1490 nm

• 1510 nm

• 1530 nm

• 1550 nm

• 1570 nm

• 1590 nm

• 1610 nm

Passive Optical

Active OpticalLine

Interf.

Power2Power1

gray

violet

blue

green

yellow

orange

red

brown

53

Modular xWDM System

Configurable Channels (Local Interface)

Fiber Wavel. Speed

MM 850 nm 1.25 Gbps

SM 1300 nm 1.25 Gbps

SM 1300 nm 2,48 Gbps

Passive Optical

Active OpticalLine

Interf.

Power2Power1

54

Optical drop/insert mux

55

Multicast

Drop and continue – optical splitter pipes

IPTV multicast Broadband Video – put them all on the

one wave-length

56

57

58

59

60

61

62

63

64

65

66

67

GMPLS: Technologies for Dynamic Optical Networks

GMPLS standards are still evolving for optical networks Growing interest for dynamic lightpath configurations Meriton’s path management includes a number of GMPLS concepts

OSPF routing on NEs (used for management network today) GMPLS LMP for auto network discovery, lightpath testing, and cable mis-

wiring Meriton will implement GMPLS in step with customer’s key

requirements for mesh networking Pre-provisioned shared protection (enabled by GMPLS signaling) Dynamic (best-effort) signaled protection Operator signaled lightpaths (S-LPs) Client on-demand wavelengths (O-UNI signaling)

Participation in initiatives such as Internet2 HOPI, CANARIE UCLP, etc., is critical