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Optical Networking Trends & Evolution

This document discusses trends and evolution in optical networking technologies. It summarizes key requirements and developments in areas like channel coding and modulation, the optical layer including line systems and switching, and protocols and multi-layer integration. For channel coding and modulation, developments that will enable higher spectral efficiencies and capacities like 400G and 1T are discussed. The optical layer section examines advances in amplification, transient suppression, and reconfigurable optical add-drop multiplexers. The protocols section evaluates the evolution of OTN, Ethernet, and MPLS-TP for multi-layer network integration.

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Optical Networking Trends & EvolutionChristoph GlingenerMarch 2011
Optical Networking Trends & EvolutionOutlineTechnology status and evolutionCoding & ModulationOptical LayerProtocols & multi-layer integrationManagement & ControlCoding&Modulation Optical Layer Protocols / Multi-Layer Management/ControlSDOCDCFROADMH-Amp100GG.709OSSEthernetMTOSIGMPLSMulti-layerSolution requirements – system/component technologies – costs !
Channel Codingand ModulationCurrentandfuturekeyrequirementsTodayMostly 10G OOK40G was a transition step to coherent, DSP-based technologiesOOK, DPSK, DQPSK, PM-QPSKCommercial success and further lifetime questionable !PM-QPSK 100G coherent (1st generation) picking upWhat‘s next ?400G, 1T ?Maximise spectral efficiency vs. reach ?Minimise costs !Get flexibility by Software Defined Optics (SDO)TodayRS-FECConcat.-FECTurbo S-FECchannelcodingandmodulation?OOKDBDPSKPM-QPSK2.5G10G40G100G
Channel Codingand ModulationRelative COGS oftransponders100G cohnormalized on 2011 10G costneedstobeadressed !Cost efficiency of 40G questionable – need low cost 100G option !
CodingAdd. NCG smaller vs. increasing OH1 dB add. by soft-in decodingModulationsingle pol., SSMF, 100km spans, ideal Raman, no DC, WDM with 5 channelsChannel Codingand ModulationWherearethelimits ?149813712611510493827160505101511.11.21.3Shannon limitGaussianch.fibercapacitylimit [1]500kmShannon limitfor ideal FEC256QAMShannon limitsoft2000km2 bithard64QAM8000kmSpectral Efficiency (bits/s/Hz)Net CodingGain [dB] for BER=1e-1516QAM100G implementations8PSKQPSKShannon limitGaussianchannelG.709BPSK-1.520251.41.5transmission rateSNR/bit (dB)[1] Essiambre, et al., “Capacity Limits of Optical Fiber Networks,” JLT, vol. 28, no. 4, Feb. 2010.Scale by Superchannel/OFDM & spatial diversity (polarization/fiber)
Channel Coding and ModulationWhat do we need to get there ?High speed DSPs/DACs/ADCs : power limitation !Photonic IntegrationPhotonics are dominating optical transceiver size & costOptions : InP, hybrid, CMOS photonicsAdapted from Fujitsu Microelectronics≈1 mmOclaro : 40 Gb/s InP DQPSK Encoding Chip
Channel Coding and Modulation400G ?480 Gb/s (incl. 15% FEC OH)Nyquist WDM spectral shapingTotal BW = #subcarriers x symbol rateOnly noise limitations consideredOverall power remains constantChannel granularity: 50 GHzPM-64QAMCapacity x reach = const.PM-8QAMPM-QPSKPM-16QAMPS-QPSK100GPM-QPSK
Channel Coding and Modulation1T ?1200 Gb/s (incl. 15% FEC OH)Nyquist WDM spectral shapingTotal BW = #subcarriers x symbol rateOnly noise limitations consideredOverall power remains constantChannel granularity: 50 GHzCapacity x reach = const.PM-16QAMPM-8QAMPS-16QAMPM-QPSK100GPM-QPSK
Channel Codingand ModulationµWave Radio (fixed) EvolutionSDR, AMCAdaptive Modulation andCoding1970198019902000XPICCross PolarizationInterferenceCanceller (see PM)Analogue AM/FM0.5/0.2 Bit/s/HzReq. S/N @ BER 1E - 3[dB]Net Efficiency [Bit/s/Hz]QPSK1/22QPSK3/4216QAM3/4416QAM5/64QPSKuncoded216QAM1/2416QAMuncoded464QAM1/2664QAM2/3664QAM3/4664QAM5/6664QAMuncoded6128QAM5/67256QAM5/68Code rateBit/SymbolNote : only convolutional coding consideredSource : Detecon
Channel Codingand ModulationµWave Radio – Adaptive Modulation & Coding (AMC)AMC to offer variable link ranges, data rates, availability @ BER 1E-11All overhead considered16-QAM, 25 min non-availability/year VBRCBR64-QAM, 115 min non-availability/year UBRVBRCBR4-QAM, 5 min non-availability/year CBRHitless switchingBetween PHY modesFIXED sliced spectrum givenSource : Marconi (now Ericsson)Hitless AMC for flexible usage of a FIXED sliced spectrum
Channel Coding and ModulationSoftware-Defined Optics (SDO) ?Reach [km]110012525002505000500350Basebandprocessor:Equalizer,Modem,SD-FECBasebandprocessor:Equalizer,Modem,SD-FECDACDAC64-QAMProgrammable400Gb/slinecard300IQ-Mod xIQ-Mod x32-QAMDACDAC25049-QAM16-QAM200LO laserLO laser25-QAMDACDAC8-QAMData Rate [Gb/s]150400Gb/sIFIF#130 Gbaud15% SD-FEC50-300 Gb/s9-QAMIQ-Mod yIQ-Mod y100DACDAC4-QAMLO laserLO laser50OTL4.4x3DPSKADCADC0IQ-xCoherentRXIQ-yIQ-xCoherentRXIQ-y-5051015OSNR Margin [dB]ADCADCOTNProc. &Mux.ADCADCQPSKADCADCIF#230 Gbaud15% SD-FEC50-300 Gb/s16QAM
Exploitation of excess system marginIncreased capacity on shorter pathsBetter utilization on spectral resources, less interfaces0.25100G150G200G0.20.15Percentage of Routes0.10.050Source : DICONET Project50060070080090010001100120013001400Channel Coding and ModulationReach variation – SDO ExampleLink Length [km]
Channel Codingand ModulationSummarySoftware Defined OpticsNot fixed at 400G, 1T – fix/slice the spectrum !Adaptive Modulation & Coding (AMC)Universal Core Interface ?Component NeedsHigh Speed integrated ADCs/DSPs/DACsPhotonic Integration !… keep questioning the requirementsIs maximum spectral efficiency and reach the dominant goal ?Costs ? churn rates ? fiber shortage ?TodayRS-FECConcat.-FECTurbo S-FECchannelcodingandmodulationSDOOOKDBDPSKPM-QPSK2.5G10G40G100G
Optical Layer – Line SystemCurrentandfuturekeyrequirementsToday‘scorelinesystem design targetsC-band, 96chs, 100Gb/sPM-QPSK Coherent, 2000+ kmSupported by optical amplificationLow nonlinear fiber signal degradationRaman booster & pre-amplifierImproved OSNRHybrid Raman + EDFA pre-amplifierWhat‘snext ?Reduce lossesImprove OSNR performanceIncrease transient suppressionTodayopticallayergain/power controlvariable gaincontrol?linesystem8 ch96 ch non-DCx160 ch C+LEDFARamanhybrid
Optical Layer – Line SystemFully integrated EDFA/Raman amplificationPerformance of different hybrid amplifiersImproved net noise figures by hybrid amplification
Gain controlled Output power=+21dBm & NF=4.5dB Transient event =1usec & Add/Drop=16dB Gain excursion<1.5dBSelf saturated Output power=+21dBm & NF=4.5dB Transient event =1usec & Add/Drop=19dB Gain excursion<0.4dBOptical Layer – Line SystemTransient suppressionIncreased transient suppression by fill lasers or self-saturation
Optical Layer – Line SystemSummaryFlexibility, enhanced system margin supported byReduced lossesROADM design, low loss fiber ?Improved OSNRHybrid amplificationIncrease transient suppressionSelf-saturated EDFAsFast VOA integrated with EDFAsComponent needs :High power pump sourcesLow relative intensity noise Raman pump sourcesTodayoptical layergain/power controlvariable gain controlTransient immune,hybrid amplificationline system8 ch96 ch non-DCx160 ch C+LEDFARamanhybrid
Optical Layer - SwitchingROADM - Functional DefinitionsColorlessDirectionlessContentionlessFlexgridColorlessDirectionlessContentionlessColorlessDirectionlessDirectionlessFixed A/DWSSWSSWSSWSSWSSLineWSSWSSWSSWSSWSSWSSWSSWSSWSSWSSWSSWSSWSSWSSWSSWSSWSSWSSA/DWDMWSSWDMWSSWSSTXTXTXTXTXLocal channels fixed in color and directionAny direction
Local channels fixed in colorAny direction
Any color
Individual color only per A/D path Any direction
Any color
Color re-use on same A/D pathAny direction
Any color
Color re-use on same A/D pathFlexible channel Bandwidth1xN WSS, Flexgrid1xN WSS1xN WSSWSSWSSWDM
Optical Layer – SwitchingCurrentandfuturekeyrequirementsFunctional Requirements8 degrees, scalableFull A/D capacity, scalableColorless – Directionless - ContentionlessFlexgrid – max. 80/96 channels @ 50 GHzNo single-point-of-failure (SPOF)Ease-of-usePhysical RequirementsMinimum loss, SNR degradation, crosstalkOptimum filtershape (cascading)Switching time ?Todayoptical layer100 GhzFlexgrid50 Ghz?switchingcolorlesscontenionlessdirectionlessFOADM2D-ROADMMD-ROADM
……Optical Layer - SwitchingROADMs … andthisishowitcouldlooklikeIL = 9 dBPer degreeNo single-point-of-failureScalable in directions and A/D capacityMinimum lossIL = 9 dB……Here : Twin WSS architectureCould be splitter (check IL and Isolation)1x16 WSS1x16 WSSLine9 portsUp to 96 channels per port… but : all WSS need to beFlexgrid and are not available todayIL = 6 dBA/D1x4 Comb1x4 Comb……Scaling to reach full add/drop capacityw/o only 25% A/D capacity(need 768:24 = 32 feeds !)passive fiberarrangementIL = 1 dB…IL = 9 dB8 x24 WSS8 x24 WSS100% add/dropcapacity for all degrees(768 ch.)…
Optical Layer - SwitchingROADMs … it‘s all aboutcompromises !IL = 6 dBRestrict to max. 6 degrees …… or scale with couplersOn line side or WSS output sideInsertion Loss !!!Per degreeIL = 6 dB…………1x9 WSS1x9 WSSLine4 portsUpto 96 channels per portMany different options (incl. reduction of A/D capacity)Cascading WSSsCombining WSS and multicast switches (PLC)Monolithic switch plus splitter and filters…Insertion Loss : in any case multiple amplifiers included !A/D
Optical Layer – SwitchingExample :MD – CDCF ROADM1x9 Line moduleA/D 1st stageA/D 8-channel IFEDFA-RAMANEDFA-RAMANSHUFFLE
Optical Layer – SwitchingSummaryCDCF ROADMs are here today !Ideal components not available todayRealization with supporting technologies possibleAvoid internal amplification as much as possibleEnsure steep passbands, proper isolationComponent needs :Line side WSS : 1xN Flexgrid with N as large as possibleA/D WSS : NxM with M as large as possibleOptical Power MonitoringMust be Flexgrid tooNeeded on line and add/drop sitesTodayopticallayer100 GhzFlexgrid50 GhzNG-CDCFswitchingcolorlesscontenionlessdirectionlessFOADM2D-ROADMMD-ROADM
Protocols and Multi-Layer IntegrationCurrent and future key requirementsG.709 / OTNScalable wrapping, multiplexing and switching technology Evolved to be more Ethernet friendlyODUflex support channelization of TDM & packet interfacesHitless resizing provides for in-service channel sizingNeed to support future bitrates and transparent timingEthernet, MPLS-TP, MPLSAll evolving and having their playMulti-layer integration is the key challengeTodayT-MPLSMPLS-TP?transportpacketEFMCFMY.17311G10G40G/100GProtocols?SONETSDHTDMG.709v3G.709v1G.709v2
Includesrichprotection, OAM optionsPlus richandevolvingprotection, OAM, … standards (802.1/2/3,Y.1731,…)Protocolsand Multi-Layer IntegrationOTN+ETH PHY evolution
Protocols and Multi-Layer IntegrationMPLS-TP and EthernetBoth, Ethernet and MPLS extended with Transport Profiles (TP)OAM, protection, traffic engineering, static and dynamic options, …Comparison is difficultMPLS-TP might have benefits in MPLS interworking (but …)Ethernet is the data link layer, always !The clever bit is to ensure seamless interworkingMPLS, VPLSService VLANMPLS PWTunnel VLANLink VLANMPLS LinkEthernet, GFPODU switchingOTN Framing, FEC, OAMOptical switching and transportMultiple options to achieve the same !
Protocolsand multi-layerintegrationMulti-layer network study - resultsUS, 46 Nodes, 18 Tb/s, 1:1 packet:TDM-> 2:110GbE (grey)…OTU2 (grey)typicalrange23%savings…PacketSwitch(MPLS)OTU2 (grey)…10GbE (grey)…10GbE (grey)…OTU2 (grey)…Hybrid Packet/Circuit Switch (MPLS/ODU)…OTU4(grey)PacketSwitch(MPLS)CircuitSwitch (ODU)CircuitSwitch (ODU)OTU4(colored)……96 lDWDM96 lDWDMContentionlessMD-ROADMOTU4(colored)OTU4(colored)…………96 lDWDM96 lDWDM96 lDWDM96 lDWDMContentionlessMD-ROADMContentionlessMD-ROADMUp to 23% savings with an integrated switchAutenrieth, et.al., “Benefits of Integrated Packet/Circuit/Wavelength Switches in Next-Generation Optical Core Networks”, NFOEC 2011, NMC4