《光纤通信课程设计》课件：Class11-03

FiberOpticNetworkDesignX.Wu,M.Y.Li,C.S.YanDept.ofOpt.Engr.,ZJU2011Class11

WDM/DWDMhistorySystemConcernsChannelspacingv.s.crosstalkGaintiltOtherissuesExerciseMultiplexingMultiplexingaprocesswheremultipleanaloguemessagesignalsordigitaldatastreamsarecombinedintoonesignaloverasharedmediumTypesTimedivisionmultiplexingFrequencydivisionmultiplexingOpticallyTimedivisionmultiplexingWavelengthdivisionmultiplexingWhatisDWDM?DefinitionDensewavelengthdivisionmultiplexing(DWDM)isafiber-optictransmissiontechniquethatemployslightwavelengthstotransmitdataparallel-by-bitorserial-by-characterHowdoesDWDMfairbetter?NoO-E-OrequiredProtocol&BitRateindependenceIncreasedoverallcapacityatmuchlowercostCurrentfiberplantinvestmentcanbeoptimizedbyafactorofatleast32TransparencyPhysicallayerarchitecturesupportsbothTDManddataformatssuchasATM,GigabitEthernet,etc.ScalabilityUtilizeabundanceofdarkfibersinmetropolitanareasandenterprisenetworksCapacityExpansionAddDWDMcapabilitytoopenuntappedembeddedcapacityMaximizereturnonembeddedfiberandTDMinvestmentEstablishandinfrastructureforlongtermgrowthAddcapacityonlywhereyouneeditAddhigherbitrateTDMsystemstoDWDMinfrastructureasnecessaryMaximizeavailablecapacity“Grow-as-you-go”investmentGracefulevolutiontomaturehigherbit-ratetechnology197519801985199019952000OpticalFibreSDHDWDMTimeline2005CWDM2008EvolutionofDWDMLate1990’s1996DWDMEarly1990’sNarrowbandWDM1980’sWidebandWDM16+channels100~200GHzspacing2~8channels200~400GHzspacing2channels1310nm,1550nm64+channels25~50GHzspacingProblem:

DemandformassiveincreasesincapacityImmediateSolution:

DenseWavelengthDivisionMultiplexingLongertermSolution:

OpticalFibreNetworksProblemsandSolutionsWavelengthDivisionMultiplexingDenseWDMMultiplechannelsofinformationcarriedoverthesamefibre,eachusinganindividualwavelengthAcommunicateswithXandBwithYasifadedicatedfibreisusedforeachsignalTypicallyonechannelutilises1320nmandtheother1550nmBroadchannelspacing,severalhundrednmRecentlyWDMhasbecomeknownasCoarseWDMorCWDMtodistinguishitfromDWDMWavelengthDivisionMultiplexerWavelengthDivisionDemultiplexerl1Al2Bl1Xl2Yl1+l2FibreWDMOverviewMultiplechannelsofinformationcarriedoverthesamefibre,eachusinganindividualwavelengthAttractivemultiplexingtechniqueHighaggregatebitratewithouthighspeedelectronicsormodulationLowdispersionpenaltyforaggregatebitrateVeryusefulforupgradestoinstalledfibresRealisableusingcommercialcomponents,unlikeOTDMLoss,crosstalkandnon-lineareffectsarepotentialproblemsWavelengthDivisionMultiplexerWavelengthDivisionDemultiplexerl1Al2l3BCl1Xl2l3YZl1+l2+l3FibreWDMOverviewTypesofWDMWavelengthmultiplexertypesinclude:FibrecouplersGratingmultiplexersWavelengthdemultiplexertypesinclude:SinglemodefusedtapercouplersGratingdemultiplexersTunablefiltersGratingMultiplexerDemultiplexerGratingGrinRodLensFibresl1l2l1+l2WDMMultiplexers/DemultiplexersMultiplexerOpticalOutputSpectrumArtO'Hare,CNET,PTLMay1996160Gbits/s8channels,20Gbits/seachGratingmultiplex/demultiplex4nmchannelspacing1533to1561nmband238kmspan3opticalamplifiersusedEarlyDWDM:CNET160Gbits/secWDMBufferedFibreonReelsOpticalTransmittersEarlyDWDM:CNETWDMExperimentalSetupDenseWavelengthDivisionMultiplexingMultiplechannelsofinformationcarriedoverthesamefibre,eachusinganindividualwavelengthDenseWDMisWDMutilisingcloselyspacedchannelsChannelspacingreducedto1.6nmandlessCosteffectivewayofincreasingcapacitywithoutreplacingfibreCommercialsystemsavailablewithcapacitiesof32channelsandupwards;>80Gb/sperfibreWavelengthDivisionMultiplexerWavelengthDivisionDemultiplexerl1Al2l3BCl1Xl2l3YZl1+l2+l3FibreDenseWavelengthDivisionMultiplexingMultiplechannelsofinformationcarriedoverthesamefibre,eachusinganindividualwavelengthUnlikeCWDMchannelsaremuchclosertogetherTransmitterT1communicateswithReceiverR1asifconnectedbyadedicatedfibreasdoesT2andR2andsoonWavelengthDivisionMultiplexerWavelengthDivisionDemultiplexerl1T1l2lNT2TNl1R1l2lNR2RNSource:Master7_4l1+l2...lNFibreSimpleDWDMSystemMultiplexerOpticalOutputSpectrumforan8DWDMchannelsystem,showingindividualchannelsSource:Master7_4SampleDWDMSignalDenseWDMisWDMutilisingcloselyspacedchannelsChannelspacingreducedto1.6nmandlessCosteffectivewayofincreasingcapacitywithoutreplacingfibreCommercialsystemsavailablewithcapacitiesof32channelsandupwards;>80Gb/sperfibreAllowsnewopticalnetworktopologies,forexamplehighspeedmetropolitianringsOpticalamplifiersarealsoakeycomponentSource:Master7_4DWDM:KeyIssues1.1Tbits/sectotalbitrate(morethan13milliontelephonechannels)55wavelengthsat20Gbits/seceach1550nmoperationover150kmwithdispersioncompensationBandwidthfrom1531.7nmto1564.07nm(0.6nmspacing)TerabitTransmissionusingDWDMExpansionOptionsInstallmorefibreNewfibreisexpensivetoinstall(Euro100k+perkm)Fibreroutesrequirearight-of-wayAdditionalregeneratorsand/oramplifiersmayberequiredInstallmoreSDHnetworkelementsoverdarkfibreAdditionalregeneratorsand/oramplifiersmayberequiredMorespaceneededinbuildingsCapacityExpansionOptions(I)InstallhigherspeedSDHnetworkelementsSpeedsaboveSTM-16notyettrivialtodeploySTM-64pricepointshavenotyetfallensufficientlyNovisibleexpansionoptionsbeyond10Gbit/sMayrequirenetworkredesignInstallDWDMIncrementalcapacityexpansionto80Gbits/sandbeyondAllowsreuseoftheinstalledequipmentbaseCapacityExpansionOptions(II)DWDMAdvantagesandDisadvantagesGreaterfibrecapacityEasiernetworkexpansionNonewfibreneededJustaddanewwavelengthIncrementalcostforanewchannelislowNoneedtoreplacemanycomponentssuchasopticalamplifiersDWDMsystemscapableoflongerspanlengthsTDMapproachusingSTM-64ismorecostlyandmoresusceptibletochromaticandpolarizationmodedispersionCanmovetoSTM-64wheneconomicsimproveDWDMAdvantagesDWDMcangiveincreasesincapacitywhichTDMcannotmatchHigherspeedTDMsystemsareveryexpensiveDWDMversusTDMNotcost-effectiveforlowchannelnumbersFixedcostofmux/demux,transponder,othersystemcomponentsIntroducesanotherelement,thefrequencydomain,tonetworkdesignandmanagementSONET/SDHnetworkmanagementsystemsnotwellequippedtohandleDWDMtopologiesDWDMperformancemonitoringandprotectionmethodologiesdevelopingDWDMDisadvantagesDWDMinstalledonalargescalefirstintheUSAlargerproportionoflonger>1000kmlinksEarlieronsetof"fibreexhaust"(saturationofcapacity)in1995-96MarketisgatheringmomentuminEuropeIncreaseindatetraffichasexistingoperatorsdeployingDWDMNewentrantsparticularlykeentouseDWDMinEuropeNeedascaleableinfrastructuretocopewithdemandasitgrowsDWDMallowsincrementalcapacityincreasesDWDMisviewedasanintegralpartofamarketentrystrategyDWDM:CommercialIssuesDWDMStandardsSource:Master7_4ITURecommendationisG.692"Opticalinterfacesformultichannelsystemswithopticalamplifiers"G.692includesanumberofDWDMchannelplansChannelseparationsetat:50,100and200GHzequivalenttoapproximatewavelengthspacingsof0.4,0.8and1.6nmChannelslieintherange1530.3nmto1567.1nm(so-calledC-Band)Newer"L-Band"existsfromabout1570nmto1620nmSupervisorychannelalsospecifiedat1510nmtohandlealarmsandmonitoringSource:Master7_4DWDMStandardsWavelengthinnm120017001300140016001500SBandCBandLBand5thWindowEBand2ndWindowOBandOpticalSpectralBandsOpticalSpectralBandsTrendistowardsmallerchannelspacings,toinceasethechannelcountITUchannelspacingsare0.4nm,0.8nmand1.6nm(50,100and200GHz)Proposedspacingsof0.2nm(25GHz)andeven0.1nm(12.5GHz)Requireslasersourceswithexcellentlongtermwavelengthstability,betterthan10pmOnetargetistoallowmorechannelsintheC-bandwithoutotherupgradesWavelengthinnm1550155415511552155315530.8nmChannelSpacingSpeedofLightassumedtobe2.99792458x108m/s

AllWavelengthsinnm1552.521552.931553.331553.731554.131554.541554.941555.341555.751556.151556.551556.961557.361557.771558.171546.521546.921547.321547.721548.111548.511548.911549.321549.721550.121550.521550.921551.321551.721552.121540.561540.951541.351541.751542.141542.541542.941543.331543.731544.131544.531544.921545.321545.721546.121534.641535.041535.431535.821536.221536.611537.001537.401537.791538.191538.581538.981539.371539.771540.161528.771529.161529.551529.941530.331530.721531.121531.511531.901532.291532.681533.071533.471533.861534.251558.581558.981559.391559.791560.201560.61SocalledITUC-Band81channelsdefinedAnotherbandcalledtheL-bandexistsabove1565nmITUDWDMChannelPlan

0.4nmSpacing(50GHz)SpeedofLightassumedtobe2.99792458x108m/s1552.521553.331554.131554.941555.751556.551557.361558.171546.521547.321548.111548.911549.721550.521551.321552.121540.561541.351542.141542.941543.731544.531545.321546.121534.641535.431536.221537.001537.791538.581539.371540.161528.771529.551530.331531.121531.901532.681533.471534.251558.981559.791560.61

AllWavelengthsinnmITUDWDMChannelPlan

0.8nmSpacing(100GHz)G.692RepresentationofaStandardDWDMSystemDWDMComponentsTransmittersDWDMMultiplexerPowerAmpLineAmpLineAmpReceivePreamp200kmDWDMDeMultiplexerEachwavelengthbehavesasifithasitown"virtualfibre"Opticalamplifiersneededtoovercomelossesinmux/demuxandlongfibrespansReceiversOpticalfibreDWDMSystemMux/Demuxeslnlnl+lTravellingontwodifferentpaths,bothwavesrecombine(atthesummer,S)Becauseofthelpathlengthdifferencethewavesarein-phaseCompletereinforcementoccurs,so-calledconstructiveinterferenceSourceSBAA+BConstructiveInterferencelnlnl+0.5lTravellingontwodifferentpaths,bothwavesrecombine(atthesummer,S)Becauseofthe0.5lpathlengthdifferencethewavesareoutofphaseCompletecancellationoccurs,so-calleddestructiveinterferenceSourceSBAA+BDestructiveInterferenceTwodifferentwavelengths,bothtravellingontwodifferentpathsBecauseofthepathlengthdifferencethe"Red"wavelengthundergoesconstructiveinterferencewhilethe"Green"suffersdestructiveinterferenceOnlytheRedwavelengthisselected,Greenisrejectednlnl+DlSourceSBAA+BUsingInterferencetoSelectaWavelengthl1....l5Constantpathdifference=DLbetweenwaveguidesWaveguidesOutputfibresInputfibreAllofthewavelengthsl1....l5travelalongallofthewaveguides.ButbecauseoftheconstantpathdifferencebetweenthewaveguidesagivenwavelengthemergesinphaseonlyattheinputtoONEoutputfibre.Atallotheroutputfibresdestructiveinterferencecancelsoutthatwavelength.l1l5CouplerArrayWaveguideGratingOperation:DemultiplexingArrayWaveguideGratingMux/DemuxAnArrayWaveguideDemuxconsistsofthreeparts:1ststarcoupler,Arrayedwaveguidegratingwiththeconstantpathlengthdifference2ndstarcoupler.Theinputlightradiatesinthe1ststarcouplerandthenpropagatesthroughthearrayedwaveguideswhichactasthediscretephaseshifter.Inthe2ndstarcoupler,lightbeamsconvergesintovariousfocalpositionsaccordingtothewavelength.Lowloss,typically6dBArrayWaveguideOperationTypicalDemuxResponse,withTemperatureDependenceDWDMSystemsTransmittersDWDMMultiplexerPowerAmpLineAmpLineAmpReceivePreamp200kmDWDMDeMultiplexerEachwavelengthbehavesasifithasitown"virtualfibre"Opticalamplifiersneededtoovercomelossesinmux/demuxand

longfibrespansReceiversOpticalfibreDWDMSystemTransmittersDWDMMultiplexerPowerAmpLineAmpReceivePreamp200kmDWDMDeMultiplexerEachwavelengthstillbehavesasifithasitown"virtualfibre"WavelengthscanbeaddedanddroppedasrequiredatsomeintermediatelocationReceiversAdd/DropMux/DemuxOpticalfibreDWDMSystemwithAdd-DropEDFAsEnableDWDM40-80kmTerminalRegenerator-3R(Reamplify,ReshapeandRetime)Terminal120kmTerminalTerminalEDFA-1R(Reamplify)TerminalEDFAamplifiesalllsTerminalTerminalTerminalTerminalTerminalManufacturer&SystemNumberofChannelsChannelSpacingChannelSpeedsMaximumBitRateTb/sNortelOPtera1600OLS1600.4nm2.5or10Gb/s1.6Tbs/sLucent402.5AlcatelMarconiPLT40/80/16040/80/1600.4,0.8nm2.5or10Gb/s1.6Tb/sTypicalDWDMSystemsDifferentsystemssuitnationalandmetropolitiannetworksTypicalhigh-endsystemscurrentlyprovide:40/80/160channelsBitratesto10Gb/swithsome40Gb/sInterfacesforSDH,PDH,ATMetc.Totalcapacityto10Tb/s+C+LandsomeSbandoperationSystemsavailablefromNEC,Lucent,Marconi,Nortel,Alcatel,Siemensetc.DWDMPerformanceasof2008upto600-700kmLLRP160-200kmRP700+kmRLLP3RRegenAnimationPower/BoosterAmpReceivePreampLineAmpPRLOpticalAmplifiersDWDMSystemSpansITURecommendationisG.692"Opticalinterfacesformultichannelsystemswithopticalamplifiers"G.692includesanumberofDWDMchannelplansChannelseparationsetat:50,100and200GHzequivalenttoapproximatewavelengthspacingsof0.4,0.8and1.6nmChannelslieintherange1530.3nmto1567.1nm(so-calledC-Band)Newer"L-Band"existsfromabout1570nmto1620nmSupervisorychannelalsospecifiedat1510nmtohandlealarmsandmonitoringDWDMStandardsAggregatespancapacitiesupto320Gbits/sec(160Gbits/secperdirection)possibleRedband=1547.5to1561nm,blueband=1527.5to1542.5nm

NortelS/DMSTransportSystemNortelDWDM8wavelengthsused(4ineachdirection).200GhzfrequencyspacingIncorporatesaDispersionCompensationModule(DCM)ExpansionportsavailabletoallowdensermultiplexingRedband=1547.5to1561nm,blueband=1527.5to1542.5nmNortelDWDMCoupler16wavelengthsused(8ineachdirection).Remains200GhzfrequencyspacingFurtherexpansionportsavailabletoallowevendensermultiplexingRedband=1547.5to1561nm,blueband=1527.5to1542.5nmSixteenChannelMultiplexing32wavelengthsused(16ineachdirection).100GhzITUfrequencyspacingPerbanddispersioncompensationRedband=1547.5to1561nm,blueband=1527.5to1542.5nm32ChannelMultiplexingDWDMTransceiversandTranspondersTransmissioninbothdirectionsneeded.InpracticeeachendhastransmittersandreceiversCombinationoftransmitterandreceiverforaparticularwavelengthisa"transceiver"DWDMMultiplexerPowerAmpLineAmpReceivePreampDWDMDeMultiplexerReceiversTransmittersDWDMMultiplexerPowerAmpLineAmpReceivePreampDWDMDeMultiplexerTransceiverDWDMTransceiversIna"classic"systeminputs/outputsto/fromtransceiversareelectricalInpracticeinputs/outputsareSDH,sotheyareoptical,wavelengtharound1550nmIneffectweneedwavelengthconvertorsnottransceiversSuchconvertorsarecalledtransponders1550nmSDH1550nmSDHCbandsignallCbandsignallTransceiversv.s.Transponders1550nmSDHCbandsignallCbandT/XSDHR/XElectricallevels1550nmSDHCbandsignallSDHT/XCBandR/XElectricallevelsTranspondersarefrequentlyformedbytwotransceiversback-to-backSocalledOptical-Electrical-Optical(OEO)transpondersExpensivesolutionatpresentTrueall-opticaltransponderswithoutOEOindevelopmentDWDMTransponders(I)Full3Rtransponders:(power,shapeandtime)RegeneratedataclockBitratespecificMoresensitive-longerrange2Rtranspondersalsoavailable:(power,shape)BitrateflexibleLesselectronicsLesssensitive-shorterrangeLuminetDWDMTransponderDWDMTransponders(II)BidirectionalTransmissionusingWDMSource:Master7_4LocalTransceiverDistantTransceiverFibresx2TransmitterReceiverReceiverTransmitterMostcommonapproachis"onefibre/onedirection"Thisiscalled"simplex"transmissionLinkingtwolocationswillinvolvetwofibresandtwotransceiversConventional(Simplex)TransmissionDifferentwavelengthbandsareusedfortransmissionineachdirectionTypciallythebandsarecalled:The"RedBand",upperhalfoftheC-bandto1560nmThe"BlueBand",lowerhalfoftheC-bandfrom1528nmRedBandFibreBlueBandReceiverl1BReceiverl2BReceiverlnBl1RTransmitterTransmitterlnRTransmitterDWDMMux/Demuxl2RReceiverl1RReceiverl2RReceiverlnRl1BTransmitterTransmitterlnBTransmitterDWDMMux/Demuxl2BBi-directionalDWDMToavoidinterferenceredandbluebandsmustbeseparatedThisseparationiscalleda"guardband"Guardbandistypicallyabout5nmGuardbandwastesspectralspace,disadvantageofbi-directionalDWDMBluechannelbandRedchannelband1528nm1560nmGuardBandTheneedforaGuardBand

TRANSMITTERAFibre,connectorsandsplicesRECEIVERBTRANSMITTERBRECEIVERAFibreCouplerFibreCouplerFrequencyFaFrequencyFbTransmitterAcommunicateswithReceiverAusingasignalonfrequencyFaTransmitterBcommunicateswithReceiverBusingasignalonfrequencyFbEachreceiverignoressignalsatotherfrequencies,soforexampleReceiverAignoresthesignalonfrequencyFbBi-directionalTransmissionusingFrequencyDivisionMultiplexingTRANSMITTERAFibre,connectorsandsplicesRECEIVERBTRANSMITTERBRECEIVERAWDMMux/DemuxWDMMux/Demux1330nm1550nmTransmitterAcommunicateswithReceiverAusingasignalon1330nmTransmitterBcommunicateswithReceiverBusingasignalon1550nmWDMMux/DemuxfiltersoutthewantedwavelengthsothatforexampleReceiverAonlyreceivesa1330nmsignalBi-directionalTransmissionusingWDMDWDMIssuesSpectralUniformityandGainTiltInanidealDWDMsignalallthechannelswouldhavethesamepower.Inpracticethepowervariesbetweenchannels:socalled"gaintilt"Sourcesofgaintiltinclude:UnequaltransmitteroutputpowersMultiplexersLackofspectralflatnessinamplifiers,filtersVariationsinfibreattenuation

152015301540155015603020100Gain(dB)EDFAgainspectrumDWDMTest:PowerFlatness(GainTilt)GainTiltandGainSlopeOutputspectrumGaintilt=5dBInputspectrumFlat:NogaintiltGainTiltExamplefora32ChannelDWDMSystemDWDMIssuesCrosstalkbetweenChannelsWithDWDMtheaggregateopticalpoweronasinglefibreishighbecause:SimultaneoustransmissionofmultipleopticalchannelsOpticalamplificationisusedWhentheopticalpowerlevelreachesapointwherethefibreisnon-linearspuriousextracomponentsaregenerated,causinginterference,called"crosstalk"Commonnon-lineareffects:Fourwavemixing(FWM)StimulatedRamanScattering(SRS)Non-lineareffectsarealldependentonopticalpowerlevels,channelsspacingetc.Non-linearEffectsandCrosstalkFourWaveMixing(FWM)Thetotalnumberofmixingcomponents,Miscalculatedfromtheformula:M=1/2

(N3-N

)NisthenumberofDWDMchannelsThusthreechannelscreates12additionalsignalsandsoon.AsNincreases,Mincreasesrapidly.....FWM:HowmanySpuriousComponents?l1l2l3l1l2l3l123l213l113l112l223l221l332l331l312l132l321l231OriginalplusFWMcomponentsBecauseofevenspacingsomeFWMcomponentsoverlapDWDMchannelsOriginalDWDMchannels,evenlyspacedFWMComponentsasWavelengthsChannelnml11542.14l21542.94l31543.743ITUchannels0.8nmspacingForthethreechannelsl1,l2

andl3

calculateallthepossiblecombinationsproducedbyaddingtwochannell'stogetherandsubtractingonechannell.Forexamplel1+l2

-l3iswrittenasl123

andiscalculatedas1542.14+1542.94-1543.74=1541.34nmNotetheinterferencetowantedchannelscausedbytheFWMcomponentsl312,l132,l221andl223FWMmixingcomponentsChannelnml1231541.34l2131541.34l3211544.54l2311544.54l3121542.94l1321542.94l1121541.34l1131540.54l2211543.74l2231542.14l3311545.34l3321544.54EqualspacingFourWaveMixingexamplewith3equallyspacedchannelsReducingFWMcanbeachievedby:Increasingchannelspacing(notreallyanoptionbecauseoflimitedspectrum)EmployingunevenchannelspacingReducingaggregatepowerReducingeffectiveaggregatepowerwithinthefibreAnothermoredifficultapproachistousefibrewithnon-zerodispersion:FWMismostefficientatthezero-dispersionwavelengthProblemisthatthe"cure"isindirectconflictwithneedminimisedispersiontomaintainbandwidthTobesuccessfultheapproachusedmustreduceunwantedcomponentlevelstoatleast30dBbelowawantedchannel.ReducingFourWaveMixingChannelnml11542.14l21542.94l31543.843DWDMchannelsAsbeforeforthethreechannelsl1,l2

andl3

calculateallthepossiblecombinationsproducedbyaddingtwochannell'stogetherandsubtractingonechannell.NotethatbecauseoftheunequalspacingthereisnownointerferencetowantedchannelscausedbythegeneratedFWMcomponentsFWMmixingcomponentsChannelnml1231541.24l2131541.24l3211544.64l2311544.64l3121543.04l1321543.04l1121541.34l1131540.44l2211543.74l2231542.04l3311545.54l3321544.74unequalspacingFourWaveMixingexamplewith3unequallyspacedchannelsChannelnml11530.00l21531.60l31533.203channels1.6nmspacingForthethreechannelsl1,l2

andl3

showncalculateallthepossibleFWMcomponentwavelengths.Determineifinterferencetowantedchannelsistakingplace.IfinterferenceistakingplaceshowthattheuseofunequalchannelspacingwillreduceinterferencetowantedDWDMchannels.Problem:SampleFWMproblemwith3DWDMchannels3channels1.6nmequalspacingFWMmixingcomponentsChannelnml11530.00l21531.60l31533.20Channelnml1231528.40l2131528.40l3211534.80l2311534.80l3121531.60l1321531.60l1121528.40l1131526.80l2211533.20l2231530.00l3311536.40l3321534.803channelsunequalspacingFWMmixingcomponentsChannelnml11530.00l21531.60l31533.40Channelnml1231528.20l2131528.20l3211535.00l2311535.00l3121531.80l1321531.80l1121528.40l1131526.60l2211533.20l2231529.80l3311536.80l3321535.20SolutiontoFWMproblemTraditionalnon-multiplexedsystemshaveuseddispersionshiftedfibreat1550toreducechromaticdispersionUnfortunatelyoperatingatthedispersionminimumincreasesthelevelofFWMConventionalfibre(dispersionminimumat1330nm)sufferslessfromFWMbutchromaticdispersionrisesSolutionistouse"Non-ZeroDispersionShiftedFibre"(NZDSF),acompromisebetweenDSFandconventionalfibre(NDSF,Non-DSF)ITU-TstandardisG.655fornon-zerodispersionshiftedsinglemodefibresReducingFWMusingNZ-DSFProvidessmallamountofdispersionoverEDFAbandNon-Zerodispersionbandis1530-1565(ITUC-Band)Minimumdispersionis1.3ps/nm-km,maximumis5.8ps/nm-kmVerylowOHattenuationat1383nm(<1dB/km)DispersionCharacteristics

LucentTrueWaveNZDSFOnewaytoimproveonNZ-DSFistoincreasetheeffectiveareaofthefibreInasinglemodefibretheopticalpowerdensitypeaksatthecentreofthefibrecoreFWMandothereffectmostlikelytotakeplaceatlocationsofhighpowerdensityLargeeffectiveAreaFibresspreadthepowerdensitymoreevenlyacrossthefibrecoreResultisareductioninpeakpowerandthusFWMReducingFWMusingaLargeEffectiveAreaFibreNZ-DSFLEAFhasaneffectivearea32%largerthanconventionalNZ-DSFClaimedresultislowerFWMImpactonsystemdesignisthatitallowshigherfibreinputpowerssospanincreasesSectionofDWDMspectrumNZ-DSFshowshigherFWMcomponentsLE