800G光模块白皮介绍

ENABLINGTHENEXTGENERATIION

OFCLOUD&AIIUSING800GB/S

OPTIICALMODULES

PROMOTERS:

Contents

1.CloudExpansionSetsPaceforOpticalModules01

2.DataCenterArchitectures03

3.8x100GSolutionforSRScenario05

3.1800GSRscenariorequirementanalysis05

3.2TechnicalFeasibilityof8x100Gsolutions05

44x200GSolutionforFRScenario

07

4.1800GFRscenariorequirementanalysis

07

4.2Technicalfeasibilityof4x200Gsolutions

08

4.3Packagingfor4x200Gsolution

09

4.4Forwarderrorcorrection(FEC)codefor200Gperlane

10

5.Possiblesolutionsfor800GDRscenario

11

6.SummaryandOutlook

12

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Sales($M)

2020

20212022

100G200G400G

2023

LIGHTCOUNTING

EnablingTheNextGenerationOf

Cloud&AiUsing800Gb/sOpticalModules

1.CloudExpansionSetsPacefor

OpticalModules

Cloudcomputingandstoragehavetakenoverasthetechnologicalbackbonetoamajorityofourmodernbusinessapplicationsprovidinginfrastructure,platform,softwareorvirtuallyanythingasaservice,andtopersonalappliancescoveringphones,laptopsandvarioussmartdevices.UnlikewirelessinfrastructureandstandardslikeLTEand5G,wherethestandardizationandtechnologyareaheadoftheactualapplications,providinga“builditandtheywillcome”businessmodel,therapidandall-encompassingexpansionofcloudapplicationsandservicesvigorouslypushesthedevelopmentofhigh-techelectronicsandoptics,whichoftenseemtorunbehindthepacesetbytheendusers.Theexponentialresourcegrowthofartificialintelligenceapplicationsandtheinherentneedforhighbandwidthforthetransportofbigdataputsafurtherstrainondatacenterarchitecturesandtheunderlyinginterconnects.Thus,thedeploymentsoftheAIcloud,aregainingmomentum.

Cloudapplications,AR/VR,AI,and5Gapplicationgeneratemoreandmoretraffic.Theexplosivegrowthoftrafficrequireshigherbandwidth.AsshowninFigure1,globalinterconnectionbandwidthcapacitywillgrowata48%CAGRin2017-2021.

WORLDWIDEGROWTH

10,000(Tbps)

CAGR:+48%

6,000

4,000

2,000

0

2020

US.EUAPLATAM

8,000

2018

2019

2017

2021

Figure1–GlobalInterconnectionIndex(Source:Equinix)

AsshowninFigure2,marketanalystsareprojectingafirstadoptionof400GDatacommodulesin2020withalargeradoptionof2x400G/800Gmodulesin2022-23.

$7,000$6,000$5,000$4,000$3,000$2,000$1,000$-

2024

2x400G

Figure2–Projectionofthemarketrevenuefordatacommodules(Source:LightCounting)

Ethernetswitchingchipcapacity

EnablingTheNextGenerationOfCloud&AiUsing800Gb/sOpticalModules

“OurLightCountingForecastmodelindicatesthatoperatorsofClouddatacenterswillneedtodeploy800Gopticsby2023-2024 tokeepupwiththegrowthofdatatraffic,”statedfounderandCEOofLightCountingMarketResearch,VladimirKozlov,PhD.“Mostof800Gwillbestillpluggabletransceivers,butweexpecttoseesomeimplementationofco-packagedopticsaswell.”

DatacentercloudarchitecturesarebeingpacedbythecapacityscalingofswitchingASICs,whichisdoublingapproximatelyeverytwoyears,unfazedbythetalkabouttheendofMoore’sLaw.Today,12.8Tb/sEthernetswitchingchipsarebeingcommerciallydeployedwithfirstchipdesignfirmsalreadyprototyping25.6Tb/ssiliconfordeploymentnextyear,asshowninFigure3.Thisputsfurtherpressureontothedensificationofopticalinterconnects,whichdonotscaleatthespeedofCMOSduetothelackofacommondesignmethodologyacrossthevariouscomponentsandacommonlargescaleprocess.

Inthepastfewyears,therapidexpansionofcloudserviceswasfueledbytherapidadoptionandpriceerosionof100Gshort

reachopticalmodulesbasedondirectdetectiontechnologyandnon-returntozero

(NRZ)modules.Afterthebeginningofthe400GbEBandwidthAssessmentactivity

inIEEEinMarch2011,initialdeploymentof400Gopticalmodulesisfinally

startingin2020withastrongerrampprojectedfor2021,asshowninFigure2.

Infact,intheinitialusecases,400Gmoduleswillbemainlyusedtotransport

4x100Gover500minDR4applicationand2x200GFR4opticsover2km,not

makinguseofthe400GbEMAC.Atthesametime,itseemsunlikelythat

IEEEwouldsoonstandardizethenextgenerationofoptics,suchas800GbE,

meaningthatthestandardizationofhigherdensityopticsforthetransportof

8x100GbEor2x400GbEforthe25.6Tb/sand51.2Tb/sswitchinggenerations

wouldbewellbehindactualmarkettimelinerequirementsof2021-22.This

raisestheneedfor800Gindustryinteroperabilityoutsideoftheestablished

standardbodies.

800G

QSFP112-DD&OSFP32x@1U/64x@2U

25.6T/51.2T

256/512Lanes

100GQSFP28

32x@1U

10GSerdes

25GSerdes

50GSedes

128Lanes

100GSerdes

128Lanes

20132015201720192021-22

400G

QSFP56-DD&OSFP

32x@1U

100GQSFP2864x@2U

40GQSFP+32x@1U

256Lanes

256Lanes

1.28T

12.8T

6.4T

3.2T

Figure3–Historicalevolutionofdatacenterswitchingchipcapacity

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EnablingTheNextGenerationOf

Cloud&AiUsing800Gb/sOpticalModules

2.DataCenterArchitectures

Thehyperscaledatacentermarketisquitefragmentedwithrespecttotheuseddatacenterarchitecturesorthedemandforpluggableoptics.DatacentersforoperatorswithalargerexternalcustomerbaseofferingXaaSaremorelikelydominatedbynorth-southclient-to-servertrafficandcouldhavemoresmallergeographicalclusters.Ontheotherhand,operatorswithalargeinternaldemandforcloudcomputingandstorageseemoreeast-westtrafficbetweenserversandcouldoperatetheirdatacentersashugeclusterswithahigherradix.Evenincaseofsimilarusecases,theoperatorscandeployindividualflavorsofnetworkarchitectureorhaveasubjectivepreferencetoacertaininterconnectssolutionsuchasPSM4orCWDM4orothercost-downvariantsofthereof,suchas100GCWDM4-OCP.

Onecanderiveatleasttwomaintypesoftypicaldatacentersarchitectures.Figure4showsthecommonabstractionofahyper-scaledatacenteranditsopticalinterconnectroadmap.Ingeneral,thesearchitecturesarelarger,haveacertainconvergencefromlayertolayer,e.g.3:1,andrelyoncoherentZRinterconnectsattheSpinelayer.Animportantboundaryconstraintfor800Gnetworkinginthiscaseisthat200Ginterconnects,albeitnotserial,areusedattheservertoTORlayer,whereastheTOR-leaf/spinelayerwouldtypicallyrelyonPSM44x200Ginafan-outconfiguration.

DC

Scenario4

.....

Spine

Scenario3

.....

Leaf

Scenario2

TOR

.....

Scenario1

Server

Scenario4

(DCI)

TypicalOpticalmoduleevolution

800G

ZR

800G

PSM4/FR4

800G

PSM8/4

200G

AOC

100GQSFP28

DWDM

400GQ-DD

ZR

40GQSFP+

eSR4/LR4

100GQSFP28

CWDM4/PSM4

400GQ-DD

DR4/FR4

Scenario3(Spine-Leaf)

40GQSFP+

SR4

100GQSFP28

SR4/PSM4

400GQ-DD

SR8/DR4

Scenario2

(Leaf-TOR)

10GSFP+

AOC/DAC

25GSFP28

AOC/DAC

100G

AOC/DAC

Scenario1(TOR-Server)

2012

2016

2019

2022

Figure4–Typicalhyperscaledatacenterinterconnectroadmap

Forthetypicalhyperscaledatacenternetwork(DCN),deploying200Gserverswillrequirean800Gfabric.It’satrafficconvergencenetwork,whichdependsonthebalancebetweenservicerequirementsandCapexoptimization.Table1showsthedetailedreachrequirementsdependingontheDCNlayer.

Spine

.....

EnablingTheNextGenerationOfCloud&AiUsing800Gb/sOpticalModules

Table1–DetailedrequirementsofthetypicalhyperscaleDCN

Scenario

ServertoTOR

TORtoLeaf

LeaftoSpine

DCI

Bandwidth

200G

800G

800G

800G

Distance

4mwithinrack;

20mcross-rack

≥70m

100mispreferred

500m/2km

80km-120km

Modulesize

QSFP-DD/OSFP

QSFP-DD/OSFP

QSFP-DD/OSFP

QSFP-DD/OSFP

Figure5showsthedatacenternetworkarchitectureofanAIcluster,withlesslayersthanthehyperscalenetworkduetothefactthatitlacksanyconvergencebetweenthelayers.ThedesignofanAIcloudimpliesdifferenttrafficflowswithmuchlargerbigdataflowsandlessfrequentswitching.

Opticalmodulerateevolution(AI/HPCCluster)

Scenario2

400G

PSM4

800GPSM8

Scenario2

(Spine-Leaf)

.....

Leaf

Scenario1

2*200GE

2*400GE

Scenario1

(Leaf-Server)

Server

2019

2021

Figure5–AI/HPCopticalinterconnectroadmap

FortheAI/HPCclusterDCN,deploying400Gserverswillrequirean800Gfabric.ThisDCNdoesn’thaveanytrafficconvergence,withfasterdeploymentthaninthecaseofFigure4.Table2showsthedetailedrequirements.

Table2–DetailedrequirementsoftheAI/HPCclusterDCN

Scenario

ServertoLeaf

LeaftoSpine

Bandwidth

400G

800G

Distance

4mwithinrack;

20mcross-rack

500m

Modulesize

QSFP-DD/OSFP

QSFP-DD/OSFP

Latency

92ns(IEEEPMAlayer)

92ns(IEEEPMAlayer)

Notexplicitlyshown,butalsorelevant,areDCnetworksforsmallercloudorenterprises,wherethedownstreamtotheserverisdecoupledfromthefan-outratesoftheLeaf-Spinelayerandtypicallyhasslowerserverinterconnectspeeds.

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MACANDHIGHERLAYERS

RECONCILIATION

400GMII400GMII

400GBASE-RPCS

400GBASE-RPCS

PMA

PMA

400GAUI-4C2M400GAUI-4C2M

PMA

PMA

800GMSA

PMD

PMD

MEDIUM

MEDIUM

EnablingTheNextGenerationOf

Cloud&AiUsing800Gb/sOpticalModules

3.8x100GSolutionforSRScenario

3.1800GSRscenariorequirementanalysis

Fortheclassof100m,theindustryisfacingthebasiclimitationsofVCSELsignalingatspeedsof100G/lane.Here,multi-modetechnologywilllikelyallowforreachesof30-50m,thusonlypartiallycoveringtheSRclass,whichisprimarilyemployedbyChinesehyperscaledatacenteroperators.TheMSAtargetsthedevelopmentofalow-cost8x100GmoduleforSRapplications,coveringthesweetspotof60-100m,asshowninFigure6.Particularly,theMSAisintendedtospecifyalowercosttransmittertechnologywiththepotentialtoleveragesub-linearcostscalingwithahighdegreeofintegration.Suchamodulewouldallowforanearlytime-to-marketdense800Gsolution.Alowcost800GSR8couldalsosupportthepotentialtrendsofanincreasingswitchradixanddecreasingservercount-per-rack,whichmaycombinetofavormiddle-of-the-rack(MoR)andend-of-the-rack(EoR)ortop-of-the-rack(ToR)architectures,byprovidingalowcostserial100Gserverinterconnect.AsshowninFigure6,theMSAwilldefinealowercostPMDforsinglemodefiberinterconnectsbasedon100GPAM4.DuetothelowlatencyrequirementsofSRapplications,KP4forwarderrorcorrection(FEC)willbeusedend-to-endwithasimpleclockrecoveryanddataequalizationunitinthemodule.Finally,theMSAwillspecifyaconnectorforthePSM8moduleswhichenablesafan-outto8x100G.

8x100G

DSP

8x100G

PSM8

Figure6–800GSR8blockdiagrams

3.2TechnicalFeasibilityof8x100Gsolutions

Asmentionedabove,signalingrateupto100Gperlanemaylimittheevolvementofmulti-modefiber(MMF)basedsolutionfrom400G-SR8to800G-SR8.BasedonthetheoreticalmodelusedinIEEE,wecanreckonthatthetransmissiondistancethatMMFcansupportisnomorethan50masthebaudrateupto50G(SeeTable3).ThelimitationfactorsarefromthelimitedbandwidthofVCSELandthemodaldispersionofMMF.Withtheoptimizationindevices,fibermediumaswellasenhancedDSPalgorithms,100mMMFtransmissionmayberealizedatthecostofhigherexpense,higherlatency,andlargerpowerconsumption.Hence,in800GPluggableMSA,werecommendthatthe800G-SR8scenarioistakenoverbySMFbasedsolution.

BER

BER

BER

FEC:KP

4

EMLon

linetest

result

EMLBERvs.OMA

10-8-6-4-202

OMA(dBm)

(a)

1.00E-021.00E-031.00E-041.00E-051.00E-061.00E-071.00E-08

1.00E-09

-

SiPh.BERvs.OMA

-10-8-6-4-202

OMA(dBm)

(b)

FEC:KP

4

SiPh.o

nlinetes

tresult

1.00E-021.00E-031.00E-041.00E-051.00E-061.00E-071.00E-08

1.00E-09

-10-8-6-4-202

EnablingTheNextGenerationOfCloud&AiUsing800Gb/sOpticalModules

Table3–FiberchannelbandwidthandtransmissiondistanceofMMFreckonedbythetheoreticalmodelusedinIEEE

Bitrate

50Gbps

50Gbps

100Gbps

100Gbps

SignalType

PAM4

PAM4

PAM4

PAM4

FiberType

OM4

OM3

OM4/OM5

OM3

Fiberchannelbandwidth(GHz•km)

2.301

1.541

2.301/2.377

1.541

Transmission

Distance(m)

100m

70m

50m

35m

IEEEstandards

50G-SR,100G-SR2

200G-SR4,400G-

SR8

Definednow

-

InordertoguaranteetheadvantagesonthecostandpowerconsumptionoftheSMFbasedsolution,reasonablePMDstandardrequirementsareindispensablein800G-SR8.ThePMDrequirementstobedefinedshouldensurethat1)diversetransmittertechniques,suchasDML,EML,andsiliconphotonics(SiPh),canbeappliedinsuchscenario;2)allthepotentialofthecomponentscanbereleasedadequatelytoachievethetargetinglinkperformance;3)keyparametersinPMDlayersshouldberelaxedasmuchaspossible,inthecontextofmaintainingareliablelinkperformance.Accordingtothesethreeprinciples,wewillconductsomebriefinvestigationsanddiscussionsasfollows.

ThepowerbudgetoftheSMFbased800G-SR8solutionwouldbequitesimilarwiththatdefinedinIEEE400G-SR8.TheonlyissuetobedeterminedistheinsertionlossofnewdefinedPSM8SMFconnectors.ItmeansthatthepowerbudgetinSRscenariocanbeachievedwithoutahitchbasedoncurrentlymatureopticalandelectroniccomponentsandDSPASICsusedin400GEopticalinterconnection.Therefore,apartfromspecifyingtheconnectorforthePSM8modules,thekeyissueforthedefinitionofPMDparametersin800SR8scenarioistofindoutthesuitableopticalmodulationamplitude(OMA),extinctionratio(ER),transmitterdispersioneyeclosurequaternary(TDECQ)ofthetransmitterandsensitivityofreceiver.Inordertosettheseparametersintothesuitableposition,thebiterrorration(BER)performanceofthediversetransmittersisinvestigatedandassessed.

DMLBERvs.OMA

FEC:KP

4

DMLo

nlinetes

tresult

OMA(dBm)

(c)

1.00E-021.00E-031.00E-041.00E-051.00E-061.00E-071.00E-08

1.00E-09

Figure7–(a)EMLBERvs.OMAresultsbasedoncommercialavailable400GDSPASICs;(b)SiliconPhotonicsBERvs.OMAresultsbasedoncommercialavailable400GDSPASICs,(c)DMLBERvs.OMAresultsbasedoncommercialavailable400GDSPASICs

Figure7showsthreeBERvsOMAcurvesof100GbpsPAM4signal,whichcorrespondtodifferenttransmittertechnologiesrespectively,asonlineresultsandobtainedusingcommercial400GDSPASICs.Actually,theBERperformancesofEMLandSiPhfor100GperlaneillustratedinFigure7(a)and(b)arewell-knownresultssincethesetwosolutionshavebeenextensivelydiscussedinthepastfewyears.ConsideringrelativelylowlaunchingopticalpowerofSiPhtransmitterandgoodenoughsensitivityofallthreesolutions,theminimumOMArequirementin800G-SR8isrecommendedtoberelaxedappropriately.

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400GBASE-R

PCS

PMA

8x112G

DSP

4x224G

PSM4

MACANDHIGHERLAYERS

RECONCILIATION

400GMII

400GAUI-4C2M

400GBASE-R

PCS

PMA

PMA

PMA

PMD

400GMII

400GAUI-4C2M

800GMSA

MEDIUM

NewPMD

EnablingTheNextGenerationOf

Cloud&AiUsing800Gb/sOpticalModules

TheBERperformanceoftheDMLinFigure7(c)showsthattheOMAsensitivityinthiscaseiscomparablewiththatinthecaseofEMLorSiPh,eventhoughthecommercialDMLusedinherehasrelativelylowerbandwidththanEMLandSiPh.ThisresultimpliesthatthecommercialDSPASICsusedinpracticehavemuchstrongerequalizationabilitythanthereferencereceiverIEEEdefinedin400GE,andthusitcansupportthetransmitterwithcomparativelylowbandwidthtoachievethetargetingpowerbudget800G-SRrequired.InordertoreleasethepotentialoftheDSPunitadequatelyfor800GSR8PMD,referencereceiverforcompliancetest(i.e.TDECQ)requirestobere-definedtomatchthepracticalequalizationabilityofcommercialDSPs,i.e.moretapsnumbersthancurrentlydefined5tapsaredesired.Meanwhile,consideringtherelativelylowsensitivityrequirementinSRscenarioandrestrictionofthepowerconsumptionofthe800Gmodule,alowcomplexityDSPmodeisrecommendedinfuturemodules.AnotherkeyparameterisERthatisrelatedtothepowerconsumptiondirectly.AlowerERisfavoredaslongasitdoesnotimpactthereliabilityofthelink.Basedontheaboveanalysis,webelievethatalowcostandpowerconsumptionSMF-basedsolutionisfeasibleandpromisingin800G-SR8scenario.

4.4x200GSolutionforFRScenario

4.1800GFRscenariorequirementanalysis

200GperlanePAM4technologyisthenextmajortechnologicalstepforopticalintensitymodulated,directdetectioninterconnectsandwillbethefoundationfora4-lane800Gconnectivity,aswellasanessentialbuildingblockforfuture1.6Tb/sinterconnects.AsshowninFigure8,theMSAwilldefinethefullPMDandpartialPMAlayersincludinganewlowpower,lowlatencyFECasawrapperontopoftheKP4FECofthe112Gelectricalinputsignals,inordertoimprovethenetcodinggain(NCG)ofthemodem.Oneofthekeygoalsofthisindustryalliancewillbethedevelopmentofnewwidebandwidthelectricalandopticalanalogcomponentsforthetransmitterandreceiverassembliesincludingdigital-to-analogandanalog-to-digital(AD/DA)converters.Inordertoachievetheaggressivepowerenveloptargetsofpluggablemodules,theDSPchipswillbedesignedinCMOSprocesswithlowernmnodeandemploylowpowersignalprocessingalgorithmstoachieveequalizationofthechannel.

8x112G

DSP

1234

Mux

4x224G

CWDM4

Figure8–800GFR4/PSM4blockdiagrams

EnablingTheNextGenerationOfCloud&AiUsing800Gb/sOpticalModules

4.2Technicalfeasibilityof4x200Gsolutions

Consideringthatatemperaturecontroller(TEC)isrequiredinLAN-WDM,whichisnotdesiredin200G/lanescenarios,thepowerbudgetwillbeanalyzedbasedonCWDM4.Linkinsertionloss,multipathinterference(MPI),differentialgroupdelay(DGD),andtransmitterdispersionpenalty(TDP)arethecontributionstothelinkpowerbudget.AccordingtothemodelreleasedinIEEEstandards,MPIandDGDpenaltyiscalculatedaslistedinTable4.Inviewoftheincreasedbaudrateof200Gperlane,thedispersionpenaltyisexpectedtobelargerthanthatin100Gperlane.Areasonablesuggestionfortransmitterdispersionpenalty(TDP)is3.9dB.Hence,takingintoaccountthemarginforreceiveragingandcouplingloss,aswellasthetypicallaunchingopticalpowervalueofthetransmitter,wethinkthereceiversensitivityrequiredshouldbearound-5dBm.

Table4–Powerbudgetanalysisof800G-FR4

Description

LinkinsertionlossMPIpenaltyDGDpenalty

TDP

Simulationvalue

4dB

0.4dB

0.4dB

3.9dB

SinceSNRdeterioratesabout3dBcomparedwith100G/laneasthebaudratedoubles,itisexpectablethatastrongerFECisnecessarytomaintainthereasonablereceiversensitivity(~-5dBm)andmarginoferrorfloor.Therefore,asmentionedabove,onthetopoftheKP4,anadditionallowpower,lowlatencyFECasawrapperwillbecarriedoutintheopticalmodule.ThethresholdvalueofthenewFECisdeterminedaccordingtothelinkperformanceandpowerbudgetrequirement.

Linkperformanceof200G/paneispresentedusingsimulationandexperiment.TheparametersofthedevicesadoptedinthelinkarelistedinTable5.TheexperimentalresultshowsthatthereceiversensitivitycanreachthetargetvaluewhilethenewFEC’sthresholdissetto2E-3asdepictedinFigure9(a).However,inthisexperiment,maximumlikelihoodsequenceestimation(MLSE)wasrequiredtocompensatetheexcessiveinter-symbol-interferenceinducedbychannelbandwidthlimitation.ThedashlineinFigure9(a)showsthesimulationbasedonthemodelinwhichthemeasuredparametersofthedevicesusedintheexperimentareadopted.Togetherwithexperimentalresults,simulationsshowthatthesystemislimitedbythebandwidthofcomponents,suchasAD/DA,driverandE/Omodulators.Consideringthathighbandwidthcomponentsareexpectedtobeavailableintheyearstocome,simulationresultsbyusingthesamesystemmodelbutwithexpandedbandwidthisillustratedinFigure9(b).Itshowsthereceiversensitivityof@2E-3canmeettheabove-mentionedrequirementwithonlyFFEequalizationintheDSPunit,whichisinaccordancewiththetheoreticalexpectation.

Table5–Parameterscomparisonbetweensimulationandexperiment

Description

3dBBandwidthofTOSA

3dBBandwidthofROSA

3dBBandwidthofAD/DAEffectiveNumberofBits(ENOB)

RIN-OMA

ChromaticDispersion

TIANoise

PDResponsivity

ValueinExperimentalSetup

42GHz

56GHz*

37GHz

4.5

~-137dB/Hz

7ps/nm

15pA/sqrt(Hz)0.5A/W

EnhancedvalueinSimulation

56GHz

56GHz

50GHz

4.5

-137dB/Hz

7ps/nm

15pA/sqrt(Hz)0.5A/W

*ROSAinexperimentsetupisahigh-bandwidthinstrument.

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SolutionB

SolutionA

Experimentvs.Simulation

Exp-FFEExp-FFE+M

LSE

Simu-FFESimu-FFE+FEC:2E-3

MLSE

FEC:KP4

-8-6-4-2024

OMA(dBm)

(a)

1.00E-05

1.00E-01

1.00E-02

1.00E-03

1.00E-04

1.00E+00

EnablingTheNextGenerationOf

Cloud&AiUsing800Gb/sOpticalModules

Basedontheaboveanalysis,TDECQisstillsuggestedtobefollowedincompliancetestinginthe800G-FR4scenario.However,FFEtapnumbersofthereferencereceiveradoptedinTDECQmeasurementisanticipatedtobeincreasedtoareasonablevalueandneedstobefurtherdiscussed.Additionally,itshouldbenotedthatiftheabilityoffuturedevicetargeting100Gbaudunderperformsourexpectation,morecomplicatedalgorithms(e.g.MLSE)maybeusedinFR4scenarios,whichimpliesthatanewcompliancemetrologymustbedeveloped.

Simulation@ExpectedParameters

8-6-4-2024

OMA(dBm)

(b)

Simu-FFEFEC:2E-3

1.00E-05

1.00E-01

1.00E-02

1.00E-03

1.00E-04

1.00E+00

-

Figure9–(a)200G/laneexperimentandsimulationresultsmatchwellwitheachother;(b)200G/lanesimulationresult:FFE

equalizationcanmeettherequirementofpowerbudgetwhencomponentbandwidthinlinkisimproved.

4.3Packagingfor4x200Gsolution

Forthe4x200Gmodule,thepackagingforboththetransmitterandreceiverneedstobereconsideredtoensuresignalintegritywithintherangeundertheNyquistfrequencypoint(56GHz).TwopossiblesolutionsforthetransmitterareillustratedinFigure10.SolutionAisatraditionalapproachwherethemodulatordriver(DRV)isclosetothemodulator.Incontrast,inSolutionB,DRVinflip-chipdesignisco-packagedwiththeDSPunittooptimizethesignalintegrityontheRFtransmissionline.Bothofthesetwosolutionscanberealizedbythestate-of-arttechnology.PreliminarysimulationsshowthatSolutionBcanachievegoodresultsandcanensureabandwidthlargerthan56GHz.TheripplesontheS21curveofSolutionAareduetothereflectiononDRVinputandcanbeoptimizedthroughthematchingdesignoftheDRV.Eventually,itisexpectedthattheoverallperformanceofSolutionAcanbefurtherimproved.

-24

-26

-28

-30

-32

-34

01020304050607080

freq.GHz

Figure10–Twopackagingsolutionsforthetransmitter.TheS21simulationputstheRFline(markedinred),thewire-bondingand

modulatorintoconsideration,andthebandwidth@-3dBoftheEMLCOCis60GHz.

KP4

KP4

800G

800G

Legacy

C2M

C2C

C2M

Concatenated

EnablingTheNextGenerationOfCloud&AiUsing800Gb/sOpticalModules

Atthereceiveside,thehighbandwidthphotodiode(PD)withlessparasiticcapacitanceandthehighbandwidthtrans-impedanceamplifier(TIA)areneededtoensurethebandwidthperformanceofthereceiver.Thereisnoobstacletorealizingthesecomponentsbythestate-of-artsemiconductortechnology.Asfarasweknow,somestakeholdersinindustryalreadyputmucheffortindevelopingthesecomponentsthataredesiredtobeavailablein1~2years.Ontheotherhand,theconnectionbetweenPDandTIAisalsocritical.Theparasiticeffectintheconnectionalwaysdegradestheperformanceandthusshouldbecarefullyanalyzedandoptimized.

4.4Forwarderrorcorrection(FEC)codefor200Gperlane

AstrongerFECwithathresholdperformanceof2E-3isrequiredtoachievethesensitivityrequirementof200GPAMreceiver.Figure11illustratesacomparisonbetweenterminatedschemeandconcatenatedscheme.Inthefirstoption,KP4isterminatedandreplacedwithanewFECwithlargeroverhead.TerminationhasadvantagesonNCGandoverhead.Inthesecondoption,aconcatenatedschemekeepsKP4astheoutercodeandcombinesitwithanewinnercode.Concatenationhasadvantagesonlatencyandpowerconsumptionandismoresuitablein800G-FR4applicationscenario.

New100G/laneAUIC2M

8

100G/laneAUI

Legacy

BER<1E-5

BER<1E-5

BER<2E-3

Terminated

KP4

NewFEC

KP4

Concatenated

KP4&newFEC

Figure11–800GFEC:TerminatedFECschemevsConcatenatedFECscheme

SerialconcatenationofKP4andanalgebraiccodeshowninFigure12isastraightforwardsolutiontoachieve2E-3BERthresholdperformance,aswellastominimizethepowerconsumptionandend-to-endlatency,sinceKP4isnotterminated.Noisewithbiterrorratepe<1E-5introducedinC2MelectricalinterfaceistransparenttoPMA.TheoverallperformanceoftheconcatenatedschemewillnotbedeterioratedbypesincepeismuchlowerthanthedecodingthresholdofKP4.HammingcodeswithsingleerrorcorrectingcapabilityandBCHcodeswithdoubleerrorcorrectingcapabilityaregoodcandidatesforthealgebraic