8/13/2019 7 DWDM

1/14

FiberS stems

DenseWavelength

Division

Multiplexing(DWDM)

8/13/2019 7 DWDM

2/14

Problemswithincreasingnetworkdemands

EvolutionofDWDM

Technicaldetails

OngoingResearch

Conclusion

8/13/2019 7 DWDM

3/14

Issues

Exponential

increase

in

user

demand

for

bandwidth Doublingofbandwidthrequirementevery69months

Consistencyinqualityofservicesprovided

Keeping

the

cost

of

solutions

at

bay

Solutions

Increasechannelcapacity:TDM,WDM

Statisticalmultiplexingofusers:Multipleopticalfibers

8/13/2019 7 DWDM

4/14

TDM (Time Division Multiplexing)TDM (Time Division Multiplexing)

Increasing bit rate to maximize utilization of givenIncreasing bit rate to maximize utilization of given

bandwidthbandwidth

WDM Wavelen th Division Multi lexinWDM Wavelen th Division Multi lexin

Use of optical fibers to achieve higher speedsUse of optical fibers to achieve higher speeds

Allow continuous channel allocation per userAllow continuous channel allocation per user

8/13/2019 7 DWDM

5/14

Dependency of MuxDependency of Mux--Demux on bit rateDemux on bit rate

how fast can we go? (Decides how small the time slots can be)how fast can we go? (Decides how small the time slots can be)

Inefficient usage of full capacity of the optical fiberInefficient usage of full capacity of the optical fiber

apa y o carry ng s gna s e c en y over s or s ances on yapa y o carry ng s gna s e c en y over s or s ances on y

Birth of Dense WDM (DWDM)Birth of Dense WDM (DWDM)

8/13/2019 7 DWDM

6/14

Late

1990s

25~50 GHz spacing25~50 GHz spacing

1996DWDM

c anne sc anne s

100~200 GHz spacing100~200 GHz spacing

Early1990s

2~8 channels2~8 channels200~400 GHz spacing200~400 GHz spacing

2 channels2 channels

Wideband WDM 1310nm, 1550nm1310nm, 1550nm

8/13/2019 7 DWDM

7/14

Definition

Densewavelengthdivisionmultiplexing(DWDM)isafiberoptic

dataparallelbybitorserialbycharacter

8/13/2019 7 DWDM

8/14

HowdoesDWDMfairbetter?

NoO

EO

required

Protocol&BitRateindependence

Increasedoverall

ca acit

at

much

lower

cost

Currentfiberplantinvestmentcanbeoptimizedbyafactor

ofatleast32

Transparency

formatssuchasATM,GigabitEthernet,etc.

Utilizeabundanceofdarkfibersinmetropolitanareasand

enter risenetworks

8/13/2019 7 DWDM

9/14

8/13/2019 7 DWDM

10/14

ransm tt ng e

Laserswithprecisestable

wavelengths OpticalMultiplexers

OntheLink

Optica

i er Opticalamplifiers

Photodetectors

OpticalDemultiplexers

Opticaladd/dropmultiplexers

8/13/2019 7 DWDM

11/14

EliminatesOEOconversions

Moreeffectivethanelectronicrepeaters

Isolatorprevents

reflection

Lightat980nmor1480nmisinjectedviathepumplaser

Gains~30dB; OutputPower~17dB

8/13/2019 7 DWDM

12/14

Dis ersion

Chromaticdispersion

Polarizationmode

dis ersion

Intrinsic:Scattering,Absorption,etc.

, , .

Fourwavemixing

Nonlinearnatureofrefractiveindexofopticalfiber

LimitschannelcapacityoftheDWDMSystem

8/13/2019 7 DWDM

13/14

MetroDWDM

CiscoSystems

e ro

o u on LucentTechnologies

LambdaXtremeTransport

WaveStarOLS

1.6T

AgilityCommunications&UCSantaBarbara

Tunable

Lasers

used

for

multiple

wavelengths

8/13/2019 7 DWDM

14/14

Robustandsimpledesign

Worksentirely

in

the

Optical

domain

Multipliesthecapacityofthenetworkmanyfold

HandlesthepresentBWdemandcosteffectively

Maximumutilizationofuntappedresources

Bestsuited

for

long

haul

networks