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Chapter 10. Designing ONS 15454 MSTP Networks

Chapter 10. Designing ONS 15454 MSTP Networks

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ONS15454MSTPDWDMDesignConsiderations

Ingeneral,DWDMdesignersandplannersmustbecognizantof

severalfactorsthatinfluencesystemtopologyand

transmissionscapability.Amongthemarephysicallimitations,

suchasstructurelocations,andfiberplanttype.Additionally,

thesystembandwidthrequirementsandscaleshouldbetaken

intoaccount,alongwiththeDWDMequipmentlimitationssuch

asamplifiernoiselimitations(OSNR)andreceiverminimum

powerlevels.

ForexistingDWDMdeployments,physicalstructurelocations

areusuallyalreadypredeterminedforamplifier/regenerator

locations.Forexample,existingDWDMsystemsmayuse60km

amplifierspacingrules;thus,becauseoutsideplantenclosures

andpowerarealreadypresentattheselocations,itisprudent

fortheDWDMdesignertoengineerthenewsystemwithinthe

presentamplifierspacingrules.Thedrawbackassociatedwith

usingexistingstructuresandspacingisthatitmightbe

economicallyinadvisableorsystematicallyimpossibletodesign

thenewDWDMsystemwithinoldphysicalconstraints.

Inadditiontophysicalstructurerequirements,whenproviding

DWDMoverexistingfiberinfrastructure,thedesignisusually

constrainedbythetransmissioncharacteristicsoftheexisting

opticalfiber.Essentially,threetypesoffiberareusedtoday:

standard,single-modefiber;nonzero,dispersion-shiftedfiber

(NZDF);anddispersion-shiftedfiber(DS-fiber).Figure10-1

detailsthetypicalattenuationandchromaticdispersionprofiles

foreachfibertype.



Figure10-1.OpticalFiberPerformanceProfile



Fromanattenuationstandpoint,DWDMC-bandandL-band

operationoccursinthelowestopticallossregionat0.21to0.25

dB/km.Themajortransmissionsdifferenceamongthefiber

typesrevolvesaroundtheirchromaticdispersioncharacteristics.

AsmentionedinChapter9,"UsingtheONS15454Platformto

SupportDWDMTransport:MSTP,"chromaticdispersioncauses

anopticalsignaltospreadintoadjacentbitperiods,whichcan

causebiterrorsatopticalreceivers.Low-costtransmitter

sources,whichtypicallyhavewidesignalspectralwidths,

exhibitmoresensitivitytothisfactoroverdistanceandtime

thanhigher-costtransmitters,whichtypicallyareconstructed

withtightersignalspectralwidths.Figure10-2illustratesthis

phenomenon.



Figure10-2.WavelengthSignalBroadening

CausedbyChromaticDispersion



[Viewfullsizeimage]



TheDS-fibermitigatesthisissuebyshiftingthezero-dispersion

parameterfromthe1310nmregiontothe1550nmregion.

Thisfacilitateslong-distance,high-bit-ratetransmissionfora

singlewavelengthat1550nmbecauseonlyopticalattenuation

isasignal-impairmentfactor.However,thezero-dispersion

propertyofDS-fibercausesmanytransmissionabnormalities

forhigh-powered,multiplexedwavelengthsinthe1550nm

region,suchasfour-wavemixing(FWM),whichmakesit

unsuitableforDWDM.

Certainfiberanomalies,suchasFWMandchannelcross-talk,

areoffsetbythechromaticdispersioneffect.However,ifthe

signalspreadstoofast,dispersioncompensationmustbeused

tocompressthewavelengthspectrumtonearitsoriginalform.

Therefore,therightbalanceofopticalpower,signalspectral

width,andchromaticdispersionisnecessaryforoptimalDWDM

distanceextension.Forsingle-modefiber(SMF),wavelength

spreadingoccursatanaveragerateof17picoseconds(ps)/nmkm;forNZDF,thetypicalchromaticdispersionrateisaround

4.4ps/nm-km.Itshouldbenotedthatthetoleranceof

chromaticdispersiondecreasesasthetransmission'sbitrate

increases.Asdetailedinthefollowingformula,eachtimedivisionmultiplexing(TDM)increaseinbandwidthresultsina

[1/16]reductionintransmissionsdistance.

(BR)2x|D|xL>104,000(Gbps)2ps/nm



Where:

(BR)isthetransmissionbitrate(suchasgigabitsper

second)

|D|istheaveragechromaticdispersionvalueforthe

transmissionwavelengthmeasuredinpicosecondsper

nanometer-kilometer(ps/nm-km)

Listhelengthofthefibermeasuredinkilometers

Thus,toincreasechannelcapacityfrom2.5Gbpsto10Gbps(a

fourfoldincrease),chromaticdispersiontolerancedecreasesby

afactorof16.

Manyotherfiber-transmissionsfactorsmustbeconsideredas

well.Theamountofpolarizationmodedispersion(PMD)infiber

canbearelevantfactorinthemaximumbitratethatcanbe

transmitted.ThePMDeffectcauseslightsignalstotravelintwo

orthogonalmodes;asaresult,aportionofthesignalpulse

travelsonafastaxis,andaportiontravelsonaslowaxis.The

downstreamopticalreceiveristaskedwithreconstructingboth

pulseaxesintoasinglebitstream.Optical-fiberPMDcanbe

causedbyanumberofelements,includingglitchesinthefibermanufacturingprocessormishandlingoffiberduringcable

manufacturingorinstallation.

Theeffectofotherfibernonlinearities,suchasstimulated

brillionscattering,stimulatedramanscattering,cross-phase

modulation,andself-phasemodulationalsomustbetakeninto

accountwhendesigningDWDMsystems;however,theseeffects

canbecontrolledwithproperequipmentdesign.

Amplifiedsystemspresenttheirowncomplexitiesintermsof

opticalsignal-to-noiseratio(OSNR)andchannelgaintilt.For

example,whenengineeringeachamplifiedspan,theDWDM



engineermustcomputetheOSNRbetweeneachspantoensure

thatthesignalleveliswithinreceiverspecificationsforeach

amplifierinuse.ThefollowingformulaisusedforOSNR

measurementforamultistageamplifier:



Where:

OSNROUTistheOSNR,indecibels,attheoutputpower

OSNRINistheOSNR,indecibels,ofthepreviousamplifier

fisthenoisefigureindecibels

hisPlanck'sconstant(6.626x1034joule-seconds)

visthefrequencyoflightinfiberat1550nm(1.935x

1014THz)

BistheBWmeasuringthenoisefigure(0.1nm)

PINistheinputpower,indecibelsreferencedto1milliwatt

(dBm),totheamplifier

Asyoucansee,manuallycomputingtheeffectsofeachfiber

transmissioneffectforeachspan/wavelengthsetcanbea

cumbersometask.Forthisreason,theONS15454MSTPis

brokenintoasetofdesignrulesforeachtopologytype.The

designrulestakeintoaccountthelimitationsofeachoptical

componentusedwithinthesystemsothattheDWDMengineer

needonlycomputetheopticalfiberlimitations,whichvaryfrom



spantospan.

Inthenextsections,youexamineasubsetofthedesignrules

associatedwitheachofthetopologiesdetailedinChapter9.



ONS15454MSTPDWDMDesignRules

Examples

Thevarioustransponder/muxponderinterfacecardsusedinthe

ONS15454MSTPexhibituniquetransmitterandreceiver

characteristics.AtypicalDWDMdesignusesawiderangeof

thesetransponder/muxponderinterfacesatvaryingbitrates.

Forreference,Table10-1detailstheONS15454MSTP

transponder/muxpondertransmissionscharacteristics.



Table10-1.ONS15454MSTP

Transponder/MuxponderTrunkOptics

Specifications



[ViewFullWidth]

Dependingonwhichtransponder/muxpondertypeisbeing

used,theopticalspandesignrulesslightlydiffer.Tables10-2

through10-4enumeratetheONS15454MSTPdesignrulesfor

thelinearandringtopologiesspecifiedinChapter9.Notethe

followingassumptions/detailsassociatedwiththedesignrules:

ThegivendesignrulescoverSMFfiberonly.

Full32-channelloadingisassumed.



Wheredispersioncompensationunits(DCUs)areplaced,

theDCUfiberattenuationisassumedtobe9dB(worst

casefortheOPT-PRE).

BothPRE/boosteramplifiersareusedonamplifiedspans.

Wherenoopticaladd/dropmultiplexers(OADMs)areused,

onlytheOPT-PREisinstalled.

Assumeequalspanlosses,withfixedOADMnodeshavinga

lossof16dB.

Theopticalpreamplifier(OPT-PRE)isengineeredfor

constantgainmodebutswitchestoconstantpowermode

whenspanlossesexceed27dB.(Thisisnotapplicableto

reconfigurableadd/dropmultiplexers[ROADM].)

Table10-2detailstheONS15454MSTPdesignrulesforlinear

networks,withoutOADMplacement.

Table10-2.ONS15454MSTPLinear(NoOADM)SpanLoss

DesignRules

10MExx.x

10MENumber (standard

xx.x

of

FEC)10E(no

Spans L1-xx.x

FEC)

(standard

FEC)



MR-L1xx.x

(standard

FEC)MRPL1-xx.x

(standard

FEC)



MR-L1xx.x(no

FEC)MRPL1-xx.x

(noFEC

DM-L1xx.xDMPL1-xx.x



MR-L1xx.x(2R,

noFEC)

MRP-L1xx.x(2R,

noFEC)



10ME-xx.x

(enhanced

FEC)10EL1-xx.x

(enhanced

FEC)



1x



35dB



25dB



37dB



33dB



30dB



37dB



2x



27dB



19dB



30dB



26dB



23dB



29dB



3x



24dB



17dB



26dB



23dB



20dB



25dB



4x



22dB



14dB



24dB



21dB



19dB



23dB



5x



21dB



22dB



20dB



18dB



22dB



6x



20dB



21dB



19dB



17dB



21dB



7x



19dB



20dB



18dB



16dB



20dB



Withthisconfiguration,thereisnoDWDMwavelengthchannel

insertion/dropcapacityatmidspannodes.Formultispansites,

themidspanshelfisconfiguredasalineamplifier.Table10-3

detailstheconfigurationthatallowsforintermediateDWDM

wavelengthchanneladd/drop.

Table10-3.ONS15454MSTPLinearwithOADMSpanLoss

DesignRules

MR-L1xx.x(no

FEC)

MRP-L1xx.x(no

FECDML1-xx.x

DMP-L1xx.x



MR-L1xx.x

(2R,no

FEC)

MRP-L1xx.x

(2R,no

FEC)



10ME-xx.x

(enhanced

FEC)10EL1-xx.x

(enhanced

FEC)



10ME-xx.x

(standard

Number

FEC)10Eof

L1-xx.x

Spans

(standard

FEC)



10MExx.x

(no

FEC)



MR-L1xx.x

(standard

FEC)MRPL1-xx.x

(standard

FEC)



1x



35dB



25dB



37dB



33dB



30dB



37dB



2x



29dB



20dB



31dB



27dB



25dB



30dB



3x



26dB



15dB



29dB



25dB



23dB



28dB



4x



24dB



26dB



23dB



20dB



25dB



5x



23dB



25dB



22dB



16dB



24dB



6x



21dB



24dB



19dB



23dB



7x



20dB



23dB



16dB



22dB



Networksthatusefixed-channelOADMsallowforplanned

DWDMchannelinsertion/deleting.However,asnotedinChapter

9,themostflexibleONS15454MSTPDWDMtopologyconsists

ofROADMs.TheROADMringandlineartopologyconfiguration

rulesareenumeratedinTable10-4.Althoughfixed-channeland

ROADMnodescancoexistinaring/lineartopology,Table10-4

addressesonlythecaseinwhichalladd/dropnodesare

configuredasROADM.

Table10-4.ONS15454MSTPROADMSpanLossDesign

Rules

10MExx.x

10MENumber (standard

xx.x

of

FEC)10E(no

Spans L1-xx.x

FEC)

(standard

FEC)



MR-L1xx.x

(standard

FEC)MRPL1-xx.x

(standard

FEC)



MR-L1xx.x(no

FEC)MRPL1-xx.x

(noFEC

DM-L1xx.xDMPL1-xx.x



MR-L1xx.x

(2R,no

FEC)

MRP-L1xx.x

(2R,no

FEC)



10ME-xx.x

(enhanced

FEC)10EL1-xx.x

(enhanced

FEC)



1x



35dB



25dB



37dB



33dB



30dB



37dB



2x



30dB



20dB



34dB



28dB



25dB



32dB



3x



28dB



17dB



32dB



26dB



23dB



30dB



4x



26dB



30dB



24dB



21dB



28dB



5x



25dB



29dB



23dB



20dB



27dB



6x



24dB



28dB



22dB



18dB



26dB



7x



23dB



27dB



21dB



14dB



25dB



8x



22dB



26dB



20dB



25dB



9x



21dB



25dB



19dB



24dB



10x



21dB



25dB



18dB



23dB



11x



18dB



24dB



17dB



23dB



12x



17dB



24dB



15dB



22dB



13x



15dB



23dB



22dB



14x



23dB



21dB



15x



22dB



21dB



ThedesignrulesummariesgiveninTables10-2,10-3,and10-4

donotrepresentthefullcapabilitiesoftheONS15454MSTP.

TheMSTPDWDMsystemisfullycapableofoperatingonNZDF

fiber,withvariouschannelcountandOADMcombinations.The

DWDMdesignengineershouldconsultthelatestinstallationand

operationsguidefortheONS15454MSTPforanexhaustivelist

ofdesignrules.







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