DOC

Spectrally

By Gordon Hart,2014-07-24 02:49
10 views 0
SpectrallySpectr

    Spectrally

SpectrallySlicedPulseSourceBasedonSupercontinuum

    ;GenerationinDispersionFIattenedPhotonicCrystalFiber

    ;XUYongzhao,ZHANGXia,HUANGYongqing.,RENXiaomin.

    ;(1.DepartmentofElectronicEngineering,DongguanUniversityofTechnology, ;Dongguan523808,CHN;2.KeyLaboratoryofOpticalCommunicationandLightwaveTechnologies

    ;MinistryofEducation,BeijingUniversityofPostsandTelecommunications,Beijing100876,CHN)

    ;Abstract:Designedisdispersion-flattenedphotoniccrystalfiber(PCF)withsmallnormaldispersionfor

    ;generatingflatwidebandsupercontinuum(SC),anddemonstratedisspectrallyslicedpulsesourcewhich

    ;utilizessupercontinuumgeneratedindispersionflattenedphotoniccrystalfiber.Theres

    ultsshowthatthefiber

    ;characterizedbyflatteneddispersionwithsmallnormaldispersionissuitableforflatwidebandsupercontinuum

    ;generation.Intheprocessofspectralbroadening,self-phasemodulationplaysadominantrole.Byfilteringthe

    ;supercontinuum,multi-wavelengthpulsescanbeobtainedoverawidespectralrange. ;Keywords:supercontinuum;dispersion;photoniccrystalfiber

    ;CLCnumber:TN253Documentcode:AArticleID:10070206(2008)03016205

    ;1IntrOductiOn

    ;Withthedevelopmentofphotoniccrystalfibers(PCFs),supercontinuum(SC)generationhasbeenthe

    ;focusofintenseresearchinrecentyearsandPCFswereproventobesuccessfulmediaforefficientSC

    ;generation.UltrawidebandlightsourcesbasedonSCgenerationhavealreadyfoundapplicationsin

    ;variousfieldssuchasopticalcoherencetomography,spectroscopy,frequencymetrologyandwavelength

    ;conversion.SCusedinopticalcommunicationisanotherattractiveapplication. ;Thereisincreasing

    ;interestinapplyingSCsourcestowavelengthdivision-multiplexing(WDM)opticaltra

    nsmission

    ;systems,forwhichmultichannelofSCpulsetrainaremodulatedascarrierwaves[5

    .Toenhance

    ;WDMnetworkswithhigherbitratesandlongertransmissiondistances,furtherresearchtoimprovethe

    ;flatnessofSCisneeded.TherequirementcanbemetbyoptimizationofthedesignofSCfiber

andthe

    ;pumpingcondition.

    ;PCFs,alsocalledholeyfibersormicrostructuredfibers,commonlyconsistofafusedsilicacore

    ;surroundedbyaregulararrayofairholesrunningalongthefiberlength. ;Theyhavetheadvantageof

    ;designflexibilityincontrollingthemodepropagationproperties[.Thechromaticdisper

    sionprofile

    ;canbeeasilycontrolledbyalteringthesizeandthearrangementofairholes.ThereforePCFsofferthe

    ;possibledesignofSCfiberwhichissuitableforSCgenerationinthete1ecommunicationwindowand

    ;meettherequirementofWDM.Inthispaper,wefocusonPCFdesignforflatandwidebandSCsource

    ;generationinthe1.55”mregion.Thedesignofadispersion—flattenedPCFispresentedand

    itisshown

    ;throughnumericalresultsthattheproposedPCFissuitableforflatandefficlentSCgenerationin

    ;Receiveddate:20080626;reviseddate:20080816

    ;Foundationitem:NationalBasicResearchProgramofChina(2003CB314906);FoundationforKeyProgramofMinistryof

    ;Education,China(104046)

    ;?

    ;162?

    ;

    ;VOI.14No.3XUYZ.eta1.SpectrallySlicedPulseSourceBasedoilSupercontinuumGenerationinDFPCF

    ;telecommunicationwindows,andthemultiwavelengthpulsesourcesbasedonspectrals

    licingofSCare

    ;alsodemonstrated.

    ;2DispersiOnnattenedPCFsDesignandSCSourceGeneration

    ;ThedecisiontousePCFsratherthanconventiona1singlemodefiberstodesignSCfiberis

    duetothe

    ;greatcontroloverthedispersionpropertiesandsimpledesigntechniqueoftheformer.Hereweutilize

    ;theadvantageouspropertiesofPCFtodesignadispersionflattenedPCFwithsmallnorm

    aldispersion.

    ;WeconsideraPCFcharacterizedbyatriangulardistributionofairfilledholeswithacentr

    a1fusedsilica

    ;core.Wehavesimulatedanumberofdifferentfiberdesignsbychangingthepitch(A)andtheairhole

    ;diameter(d)ofPCF.Afull-vectoria1solverEisusedtocalculatethefiberdispersion. ;Fig.1(a)and(b)presentsomeexamplesofflatteneddispersiondesigns.InFig.1(a),wekeepA

    ;2.42ttmwhilechangingdslightly,whereasinFig.1(b),wechangeAwhilekeeping0.59ttm.The

    ;calculationresultsshowthatthedispersioncurvemoveupwardwhilekeepingAconstantan

    dincreasing

    ;d,whereas,whilekeepingdconstantandincreasingAthedispersioncurvealsomoveupwar

    d.Fig.1

    ;indicatesthatwecanobtainaPCFwithflatteneddispersionstructureandsmallnormaldispe

    rsion

    tuningofbothAandd.Bychangingthefiberparameters,wec;throughanappropriatefine

    anadjustthe

    ;characteristicofthedispersioncurve. ;4

    ;.

    ;2

    ;

    ;0

    ;

    ;

    ;乏,2

    ;

    ;

    ;毒,4

    ;1

    ;-

    ;fh1

    ;d=05gpm

    ;{A=240um

    ;2.A241um

    ;3.A.242”m

    ;‘f}}}ll

    ;}li

    ;Fiber3Fiber2Fiber{

    ;_

    ;+

    ;iI.It’

    ;Wavelength/nmWavelength/nm ;Fig?1ExamplesofchromaticdispersionbehaviorofdispersionflattenedPCFs:(a)以一2.

    ;42m,0.584m,0.587m

    ;and0.59m(b)d=0.59m,A2,40m,2.4tmand2.42m ;PropagationofultrashortpulsesinPCFcanbedescribedbythenonlinearSchrodingereq

    uation

    ;(NSE),writtenasF1]

    ;O

;aU+a一薹P0(+)z,T):..dT’R(T);(1)

    ;WhereU(z,T)isthenormalizedenvelopeoftheelectricfield,zisthelongitudinalcoordinate

    a1ongthe

    ;fiber,Tisthetimeinareferenceframetravelingwiththepumppulse,isthe

    thorderdispersion

    ;coefficientatthecentralfrequency0,isthefiberloss,yisthenonlinearcoefficientandP

    ;nisthepeak

    handsideofEq.(1)inc1udesthechromat;poweroftheinputpulse.Thefirstitemoftheright

    ic

    ;dispersioncontributionsandlinearattenuation.Thesecondandthirditemsareresponsiblef

    ornonlinear

    ;effectsincludingself-phasemodulation(SPM),self-steepening(SST)andstimulatedRa

    manscattering

    ;(SRS).Eq.(1)canbenumericallysolvedby’usingsplit—stepFourieralgorithmandthepulse

    ;propagationissimulated.

    ;Weselectfiber3inFig.1(b)asaSCfiber,andconsiderthepropagationofthehyperbolicse

    cant

    ;inputpulsewithdurationof0.5ps(TFwHM)andacentralwavelengthof1550nm.Thevalue

    sare

    ;?

    ;163?

    ;【卜g=.gsj/IJ{ds【『Jg

    ;

    ;SemiconductorPhotonicsandTechnologyAug.2008 ;ThecalculatedresultiSshowninFig.2,inwhich ;theoutputSCspectrumwith10dBbandwidthof

    ;126nmoffersabroadenedandflattenedspectrum ;thatcanbeslicedoverawidewavelengthrange. ;Oneofthemostimportantapplicationsoftheflat ;SCgeneratedinthe1550nmbandisthedesignof ;multiwavelengthsourcesforWDMsystems.By ;slicingSCspectrum,wecanobtainmulti- ;wavelengthopticalcarriers.Here,weuseatunable ;Gaussianfiltertosliceoutpulse.Fig.3showthe ;slicedpulsefilteredoutfromSCspectruminthe ;rangefrom1510nmto1590nm.Thepulsewidths ;areapproximately4psoverallrangesandthetime ;bandwidthproductsAvAtarebetween0.43and ;0.45,whichindicatesthatthepulsesarenearly ;transformlimitedGaussianpulses.Theintensity ;variationsamongtheslicedpulsearelessthan3dB ;inthespectrumrangefrom1518nmto1587nm. ;Becausethespectrumisinthenormaldispersion

    ;region,theslicedpulseswithshorterwavelength ;laggedbehindthosewithlongerwavelength.The ;widthoftheslicedpulsedependsmainlyonthe ;Wavelength/nm

    ;FlatwidebandSCgeneratedinfiber3inFig.1(b) ;Fig.3SlicedpulsefilteredoutfromSCspectrumat ;differentwavelength

    ;passbandoftheslicingfilter.Bychangingthepassbandofthefilter,ashorteroflongerpulsetr

    ain

    ;wouldbeobtained.Ifweusearrayed-waveguidegrating(AWG)asaslicingfilter,multiw

    avelength

    ;pulsetrainscanbeobtainedsimultaneouslyandthepowerlevelsofthechannelscanbeequal

    izedwithan

    ;integrateddynamicpowerequalizer.’

    ;Becausethethirdorderdispersion(TOD)isnegligiblysmallandself-steepeningaswe11

    asRaman

    ;scatteringhavelittleinfluenceonthepulse ;propagationundernormaldispersion,thusaSC

    ;spectrumwithgoodsymmetryisgenerated.

    ;?

    ;IntheprocessofSCgeneration,self-phase ;modulation(SPM)isthedominantnonlineareffect ;responsibleforspectrumbroadening.Toinvestigate ;thegenerationofflatwidebandSC,weshowsthe ;evolutionsofeffectivepeakpowerandthe10dB

    ;spectralwidthofthepulsewithpropagation ;distanceinFig.4.Itindicatesthattheeffectivepeak ;powerdecreasesrapidlywhilethespectrumbroaden ;i

    ;{

    ;

    ;

    ;

    ;?

    ;

    ;

    ;Fig.4Evolutionsofeffectivepeakpowerand——10dB

    ;spectralwidthalongthepropagationdistance ;?p/suNLfUz?p/言营_!一日g誉乏g

    ;F

    ;了基ie(1

    ;

    ;VO1.14No.3XUYZ,eta1.SpectrallySlicedPulseSourceBasedonSupercontinuumGene

    rationi_nFP

    ;drasticallvinashortdistance,howeverthespectralwidthtendstobeinvariablejustafter0.2km

    ;becausethepeakpowerhasbeengreatlyreducedandthenonlineareffectshavebeenweakened,

    ;accordinglyalongfiberlengthisnotnecessarytogenerateabroadSC.Nevertheless,thefiberlength

    ;shouldbelongenoughtoobtainaflatSC.Thereasonisthatintheinitialstage,SPMdominatesover

    ;thedisDersionbecauseofsmalldispersion.Thereforethedramaticspectrumbroadeningisaccompanied

    ;bvanoscillatorystructurecoveringthespectralrange.Withanincreaseinpropagationdistance,the

    ;effectivepeakpowerkeepsdecreasingbutnotsorapidlyasprevious.Inthisstage,althoughthe

    ;sDectrumalmostceasestobroaden,thefluctuationsinthespectrumdiminishgraduallyandthespectrum

    ;becomesflatterwithfurtherpropagation.Eventually,thespectrumachievesgoodflatness.Inanormal

    ;disDersionfiber.thespectralbroadeningisproportionaltosolitonorderN

    (LD/LNL),whereLD

    ;/fi2isthedisPersionlengthandLNL

    1/yP0isnonlinearlength.ThusNcanbewrittenas(7P0TZo/

    ;)1/2.Forahyperbolic—secantpulseT0isrelatedtoTFwHMbyTFwHM?1.763T0.Wecan

    increasethe

    ;spectralbroadeningbyincreasingtheeffectivepeakpoweryP0,decreasingthefiberdispersionandusing

    ;pulseswithshortduration.

    ;3ExperimentalSetupandResuits

    ;TheexperimentalsetupisshowninFig.5.The

    ;fiberusedintheexperimentisan80m-long

    ;dispersion-flattenedPCFsuppliedbycrystalfiber

    ;A/S.Itscrosssectionanddispersioncurveare

    ;showninFig.6(a)and(b),respectively.Thefiber

    ;hassmallnormaldispersionandsmalldispersion

    ;slopeoverawidewavelengthrange.Thedispersion

    ;isabout0.58ps?nm?kmat1550nmand

    ;thedispersionvariationislessthan1.5ps?nm?

    ;kmbetween1500nmand1650nm.Thenonlinear

    ;coefficientis11W?km.Theattenuationofthe

    ;fiberismeasuredtobe1essthan9dB/kminthe

    ;rangeof1510nm1620nm.PCFissplicedto

    ;connectorizedpigtailfiberateachend,leadingtoa

    ;tota11ossofmorethan3.5dBat1550nm.

    ;Weusedamodelockedsemiconductor1aser

    ;operatedat1550nm.Itproduces1.6ps(FWHM) ;pulsetrainatarepetitionrateof10GHzwithan ;averagepowerof6dBm.Inorderto.avoidany

    ;retroreflectionstowardthelaser,anopticalisolator ;wasplacedjustaftertheoutputofthelaser.The ;pulseswereamplifiedwithanerbiumdopedfiber

    ;amplifier(EDFA)andcoupledintoPCF.Thepulses ;comingoutfromPCFweresplitintotwopartsbya ;couplerwith59/695powersplittingratio,and

    ;thentheywererespectivelyfedintoanoptical ;DFPCF

    ;Fig.5Experimentalsetup(DFPCF:dispersi.on-flattened ;PCF;OSA:opticalspectrumanalyzer;PM: ;powermeterandPC:polarizationcontroller) ;O

    ;

    ;l

    ;-

    ;2

    ;-

    ;3

    ;

    ;?

    ;

    ;/————\

    ;//

    ;15o0154015801620l660

    ;W~velengthMra

    ;Fig.6(a)PCFmicrostructureregion(b)PCFdispersion ;cUrve

    ;?

    ;165?

    ;

    ;Gl

    ;目匿下毒嚣dJ/u0器量益

    ;

    ;SemiconductorPhotonicsandTechnologyAug.2008 ;spectrumanalyzerandapowermeterforanalyses. ;Fig.7showsthemeasuredSCspectrumoutputfromPCF.Theaveragecoupledpowerintoth

    ePCF

    ;was35dBm.Forcomparison,theinitialspectrumoutputfromthelaserisalsoshowninFig.7

    .The

    ;generatedflatbroadbandsupercontinuumrangingfrom1503nmto1593nmhastheflatness

    of--

;+2.5dB.But

    ;itcanbenoticedthatthespectralbroadeningisaccompaniedbyanoscillatorystructurecoveringthe

    ;spectrumrange.ThosefeaturesshowapatternofSPMinducedspectralbroadening.Ifwe

    usealonger

    ;fiberlengthandashorterpulsewidth,asmootherSCspectrumcanbeobtained.Fig.8showthepulses

    ;trainfilteredoutfromSCspectrumatdifferentwavelengthes.Wecanseethattheslicedpulseshavethe

    ;samerepetitionratewiththeinitialpulse,andthepulsesourceisapplicabletosuchaspectrumsliced

    ;pulsesourceforWDMtransmissionsystems,wavelengthconversionandopticalsignalprocessing.

    ;Wavelength/nm

    ;Fig.7GeneratedSCspectrumwhen

    ;is35dBITI

    ;I}J

    ;I;i

    ;}}

    ;}}

    ;__

    ;]j

    ;ll{ljI

    ;

    ;f

    ;l{l{I

    ;mat1530nm(b),

    ;and1570nm(d)

    ;4Conclusions

    ;Inconclusion,wehavedesigneddispersionflattenedPCFswithsmallnorma1dispersio

    nforflat

    ;widebandSCgenerationinte1ecommunicationwindows.Thenumerica11yresultsshowthattheproposed

    ;fiberissuitableforflatbroadbandgeneration.IntheprocessofSCgeneration,SPMisthedominant

    ;nonlineareffectresponsibleforspectrumbroadening.Multiwavelengthpulsesourcesb

    asedonsDectral

    ;slicingoftheflatbroadbandSCaredemonstratednumerica11yandexperimenta11y ;.

    ;Keferences:

    ;L1]CoenS,ChauAHL,LeonhardtR,eta1.SupercontinuumgenerationbystimulatedRamanscatteringandparametric

    ;{ourrwavemixinginphotoniecrystalfibers[J].J.Opt.Soc.Am.B,2002,19(4):753764.

    ;[2]RaviKanthKumarVV,GeorgeAK,ReevesWH,eta1.Extrudedsoftg1assphotoniccrys

ta1fiberforultrabroad

    ;

    ;supercontinuumgeneration[J]:Opt.Express,2002,10(25):15201525.

    ;}

    3]SChreiberT,LimpertJ,ZellmerH,eta1.Highaveragepowersupercontinuumgenerationinphotoniccrysta1fibers

    ;[J].Opt.Commun.,2003,228:71,78.

    ;[4YAoLi,HELi,YANGBo-jun.

    ;Superc.ntinuumgenerati.ninn.rma1dispersi.nphotoniccrysta1fiberusing

    ;picosecondpulse[J].SemiconductorPhotonicsandTechnology,2007,13(4):256260.

    ;L5]OharaT,TakaraH,YamamotoT,eta1.Over-1000

    channelultradenseWDMtransmissionwithsuDercontinuum

    ;multicarriersource[J].IEEEJ.LightwaveTechno1.,2006,24(6):23112317.

    ;[6]xuY,RenX,WangZ,eta1.Flatlybroadenedsupercontinuumenerationat10Gbit/susingdispersion

    ;flattened

    ;photoniccrystalfiberwithsmallnormaldispersion[J].ElectronLett.,2007,43(2):8788.

    ;(Continued0page206)

    ;?

    ;166?

    ;

    ;SemiconductorPhotonicsandTechnologyAug.2008

    ;[23]HuangA,GunnC,IiGI,eta1.AlOGb/8ph.tonicm.du1at.randWDMMUX/DEMUXintegraedwih

    ;electr.nicsin0.13”mSOICMOSEA].Proceedings.ftheIEEEInt’1SolidStateCircuitsConf?,SanFranci.c.,CA,

    ;5Feb2006.

    ;[24]

    ;E25]

    ;GunnC.CMOSphotonicstechnologyplatform[A].SPIEPhotonicsWest,SPIEProceedingsvol?6125onSili..”

    ;Photonics.SanJose,CA,2006.

    ;GunnC.CMOSPhotonicsTM-SOIlearnsanewtrick[A].Proceedingsofthe2005IEEEInt’1SOIConference,

    ;Honolulu.HI.2005.

    ;Biography:

    ;XIAOXi(1983--),ma1e,anativeofHubeiprovince,China.HereceivedtheB.S. ;DegreeandMaster’sDegreefromHuazhongUniversityofScienceandTechnologyin

    ;2007.HeisnowstudyingforaPHDdegreeinInstituteofSemiconductors,Chinese ;AcademvofSciences.Hcurrentresearchinterestsareinthefieldsofsilicon ;photonics,opticalinterconnectsandopticalmicrocavities. ;Email:xixiao@red.semi.ac.cn

    ;(Continuedfrompage166)

    ;r7]FerrandoA,si1vestreE,MiretJJ,eta1.Designingaphotoniccrystalfiberwithflattenedc

hromaticdispersion[J].

    ;Electron.Lett.,1999,35(4):325327.

    ;[8]shenIP,HuangWP,ChenGX,eta1.Designandoptimizationofphotoniccrystalfibersforbroadbanddispersion

    ;compensation[J].IEEEPhoton.Tech.Lett.,2003,15(4):540542.

    ;[9]WuTI,ChaoCH.Anovelultraflatteneddispersionphotoniccrystalfiber[J].IEEEPhoton.Tech.Lett.,2005,17

    ;(1):67-69.

    ;[1O]CHENMing,YANGSigang,XIEShizhong.Newhighnonlinearanddispersionflattenedphotoniccrystalfiber[J].

    ;SemiconductorPhotonicsandTechnology,2007,13(4):252255.

    ;[11]SaitohK,KoshibaM.Fullvectorialimaginary-distancebeampropagationmethodbasedonfiniteelementscheme:

    ;ApplicationtoPhotonicCrystalFibers[J].IEEEJ.QuantumElectron,2002,38(7),9279

    33.

    ;[12]AgrawalGP.NonlinearFiberOptics[M].NewYork:AcademicPress,1995. ;Biography:

    ;?

    ;2O6?

    ;XUYongzhao(1972),male,anativeofGuangdongprovince,China.Hereceivedhis ;Ph.D.degreefromBeijingUniversityofPostsandTelecommunicationsinJuly,2007. ;HehasbeenworkinginGongguanUniversityofTechnologysince2007.Hismain ;researchint?

Report this document

For any questions or suggestions please email
cust-service@docsford.com