基于光子技术的高速可调微波开关.pdf 6页

'中国科技论文在线http://www.paper.edu.cnPhotonic-assistedMicrowaveSwitchatSpeedof<100#Picosecond**5FengXia,YanLianshan,JiangHengyun,PanYan,JiangLin,LuoBin,PanWei(CenterforInformationPhotonics&Communications,SouthwestJiaotongUniversity,Chengdu,Sichuan610031)Abstract:Aphotonicapproachtorapidlyswitchtwomicrowavesignalswithdifferentfrequencyor/andphaseisproposed.Weexperimentallyshowthattwomicrowavesignalswithapreciseπphase10differenceat21-and29.425-GHzaresuccessfullyswitchedatthespeedof93.4-,83.3-psrespectively.Keywords:microwavephtonics;microwavesignalsswitch;phasehopping;Mach-Zehnerinterferometer0Introduction15Fastmicrowavesignalsswitchisveryimportantforthenextgenerationradarsystem,[1,2]cognitiveradionetworkand5Gwirelesscommunicationsetc..Itcanpotentiallyrealizethefastphaseor/andfrequencyhoppingforsecretcommunicationinmilitary.Aftercomparedwithalltheelectricalones,photonic-assistedmicrowavesignalsswitchhastheadvantagesofwider[2,3]bandwidth,lowerloss,largerandfastertunability,anti-electromagneticinterference,etc..Until20now,severalphotonic-assistapproachestorapidlyswitchtwomicrowavesignalswithdifferencefrequencyhasbeenreportedusingthecombinationofspectralshapingandfrequencytotime[4,5]mapping,combfilterwithultra-fasttunabilityetc..However,theymerelyrealizethefastfrequencyhopping,ratherthantheboth.Fastphasehoppingishighlyrequiredforaphase-arrayantennawitharapidlyreconfigurableemitteddirection.25Inthispaper,anovelapproachtorapidlyswitchtwomicrowavesignalsisdemonstratedatthespeedof<100-ps.Asweknown,ahigh-qualitymicrowavesignalcanbephotonic-assistedgeneratedbybeatingtwocoherentopticalfrequencytonesatthephoto-detector(PD).WhenthreecoherentopticalfrequencytonesarelaunchedintothePD,twotonescanbeindependentlycontrolledtoappearornotbysettingthebitofbinarydatas′(t)being“1”or“0”,theywould30alternativelybeatingwiththeleftoneinthetimedomain.Therefore,bydynamicallymanipulatingthreeopticalfrequencytones,thetwomicrowavesignalsaregeneratedandrapidlyswitchedbasedonthebitofdatas′(t).Weexperimentallydemonstratedthattwomicrowavesignalswithapreciseπphasedifferenceat21-and29.425-GHzaresuccessfullyswitchedatthespeedof93.4-,83.3-ps.Thatis,thephasehoppingmicrowavesignalswithadifferentfrequencyof21-,29.425-Hzhave35beenachievedinourexperiment.1PrincipleTheschematicdiagramoftheschemeisshowninFig.1(a).Itconsistsofthreefrequencytones,phasemodulator(PM),Mach-Zehnderinterferometer(MZI)andphoto-detector(PD).Theinputthreefrequencytones(e.g.f1,fcandf2)areproperlyplacedinmaximum,mediumand40minimumpointofMZItransmissionfunction.AftertheMZI,thefrequencytoneoff1atmaximumpointappear(disappear),andthefrequencytoneoff2atminimumpointdisappear(appear)whenthebitofs′(t)is“0”(“1”).WhilethefrequencytoneoffcatmediumpointwouldappearalltheFoundations:SpecializedResearchFundfortheDoctoralProgramofHigherEducation(No.20130184110015)Briefauthorintroduction:FengXia(1991-),female,doctoralcandidate,mainlyinterestedinmicrowavephotonicsCorrespondanceauthor:YanLianshan(1971-),male,professor,doctoralsupervisor,mainlyinterestedintheresearchofinformationphotonics.E-mail:lsyan@home.swjtu.edu.cn-1- 中国科技论文在线http://www.paper.edu.cnway.Here,weemploythesimplestmethodtogeneratethreefrequencytonesviaopticalmodulation.Acontinuouslightwavefromatunablelasersource(TLS)issenttoaMach-Zehnder45modulator(MZM).ThenaRFsignalisappliedtotheMZMfordoublesidebandmodulation(DSM).ThenormalizedopticalfieldattheoutputoftheMZMcanbewrittenasE=exp(jt)[1+exp(jsint)](1)cRFWhereωc=2πfcandωRF=2πfRFaretheangularfrequenciesofthelight-waveandRFsignal,β=πVRF/Vπ1isthemodulationindexoftheRFsignal,VRFistheamplitudeofRFsignal,Vπ1isthe50half-wavevoltageoftheMZM.Anexpansionof(1)withBesselfunctionsasfollowingE=exp(jct)[1Jn()exp(jnRFt)](2)nthWhereJnisthen-orderBesselfunction.Whenthemodulationindexissmall,ignoringthehigherorderterms,onlythefirst-ordersidebandsareconsidered,andJ0(β)≈1,J−1(β)=−J1(β)≈−β/2,Eq.(2)55canbefurtherdescribedbyE(1J())ejctJ()ej(cRF)tJ()ej(cRF)t2ejct2ej(cRF)t2ej(cRF)tj(3)011FromEq.(3),itcanbeshownthatthephasedifferenceoftwofirst-ordersidebands(i.e.f1andf2)isπ.(f1=fc+fRF,f2=fc-fRF).Thenthelight-wavesoutputoftheMZMaresenttoaPM(oranMZM)appliedbyanbinarydatasignals(t)withabit-rateofB.Theopticalfieldattheoutputof60PMcanwrittenasEe[2ejct2ej(cRF)t2ej(cRF)tj]ist()(4)Whereγ=πVs/Vπ2isthemodulationindexofthedatasignal,Vsistheamplitudeofdatasignal,Vπ2isthehalf-wavevoltageofthePM.65Fig.1(a)Theschematicdiagramofphotonicmicrowavesignalsswitch(here,foranexample,twomicrowavesignalswithapreciseπphasedifferenceisfastswitched).(b)Thecorrespondingprinciple:Apoint:phasemodulatedsignals;Bpoint:theoutputofMZIintimedomain;DPSK:differentialphaseshiftkeying;MZI:Mach-Zehnderinterferometer;PD:photo-detector,s(t):thebinarydatasignal;s′(t):thedifferentialsignalofs(t)ThenanMZIwithtunableFSRvalueandcentralwavelengthisused,thetransmission70functionofMZIcanbeexpressedashMZI(t)=1/2[δ(t)+δ(t+τ)],whereδ(t)istheimpulsefunction,-2- 中国科技论文在线http://www.paper.edu.cnandτisthetimedelaywhichcanbetunable.AsshowninFig.1(b),fortheMZItransmissionfunction,wespecificallysetthefrequencytoneoff1(orf2)atthemaximumtransmissionpoint,thefrequencytoneoff2(orf1)attheminimumtransmissionpoint,whenf2-f1=2fRF=(n+1/2)Δfissatisfied,whereΔf=1/τ,thefreespectralrange(FSR)ofMZI.Whenthetimedelayτisequalto75thetimeofonebit(1/B),twoinvertedOOKsignalsoffrequencyf1andf2areobtainedatone[6,7]outputportofMZIintimedomain.AttheoutputofPD,thetwosidebandsbeatwithfrequencyfcalternatively,whichcanbedescribedas2it()R*{16442cos[t+((st1)st())]}(5)RFWhereRistheresponsivityofthePD.ItcanbeseenfromEq.(5),adifferentialphase80hoppingmicrowavesignalisgeneratedwithahoppingrateofB,whichiscreatedbythefastswitchoftwomicrowavesignalswithdifferentphase.Therefore,thetwomicrowavesignalscouldberapidlyswitchedbasedonthebitofdatas′(t)bydynamicallymanipulatingthreeopticalfrequencytonesinoursystem.Itcanrealizetheswitchoftwomicrowavesignalswithdifferencephase,ortwomicrowavesignalswithdifferencefrequencyortwomicrowavesignalswith85differencephaseandfrequency.Toconfirmtheproposedschemeinprevioussection,wecarryoutanexperiment.TheexperimentalsetupisshowninFig.2.Acontinuouslight-wavewiththecentralwavelengthof1549.432nmandoutputpowerof13dBmhasbeentransmittedfromaTLS(Yenista),thenissenttoanintensitymodulator(IM)(Fujitsu),andthereisapolarizationcontroller(PC1)beforetheIM90forimprovingthemodulationefficiency.ARFsignalgeneratedbyananalogmicrowavesignalgenerator(Agilent)isappliedtotheIM.Tocompensatethepowerlossinpreviouslinks,anEr-dropedopticalfiberamplifier(EDFA)withtunablegainisadded.Thebinarydatasignalisgeneratedbyapulse-patterngenerator(PPG,Anritsu,MT181),andisappliedtotheMZMfortheDPSKmodulation.TheMZIwiththetunableFSRvalueandcentralwavelengthisusedinour95experiment.Finally,theoutputsignalofMZIisdetectedbyahigh-speedPD.Moreover,anopticalbandpassfilter(OTF)withtunablecenterwavelengthandbandwidthisaddedattheinputofPD,sothatwecaneasilyseparatelychecksinglemicrowavesignalsfromthetworapidlyswitchablemicrowavesignals.Whenoneopticalsidebandisfilteredout,onlyonemicrowavesignalcanbegeneratedandrapidlyswitched.Henceanon-offkeying(OOK)signalsisobtained100attheoutputofPD.IMPC1PC2TLSEDFAMGPPGs(t)τOTFMZMPDMZIFig.2Theexperimentalsetupofthescheme:TLS:TunableLightSource,PC:PolarizationController,IM:IntensityModulator,EDFA:Er-dropedOpticalFiberAmplifier,MZM:Mach-Zehndermodulator,OTF:OpticalTunableFilter,MZI:Mach-ZehnderInterferometer,PD:Photo-detector,MG:MicrowaveSignalGenerator,PPG:105Pluse-PatternGeneratorFirstly,thefrequencyandtheoutputpowerofRFsignalaresettobe29.425-GHzand7-dBm,respectively.Thebit-rateofbinarydatasignals(t)is10.7-Gb/swithafixedpatternof”1111000”alongwiths′(t)hasafixedpatternof“10001000”ByadjustingthebiasvoltageoftheIM,theDSM-3- 中国科技论文在线http://www.paper.edu.cnisachieved.AndtheoutputsignalwaveformfromMZMintimedomainisshowninFig.3(a).The110outputsignalsfromMZIinfrequencytonesf1andf2aretwocomplementaryOOKsignalswithpattern“10001000”and“01110111”asshowninFig.3(b)and(c)respectively.Next,wetunethecenterwavelengthandbandwidthofOTFtoensureonlyoneofthetwoopticalsidebandsandopticalcarrierthrough(f1,fcorf2,fc).AttheoutputofPD,thewaveformsareshowninFig.3(d)and(e).TuningthecenterwavelengthandbroadbandoftheOTFmaketheallthreefrequency115tonesthrough(f1,f2andfc),twomicrowavesignalswithaswitchspeed10.7GHzareachievedattheoutputofPDasshowninFig.3(f).Notethat,whenthebitsofbinarysignalchangefrom“1”to“0”bitorfrom“0”to“1”bit,thereis±πphaseshiftforthedetectedphasehoppingsignal,whichisdifferentfrombinaryphaseshiftkeying(BPSK).InBPSKsignal,differentcodeisexpressedbytheRFsignalwithdifferentinitialphase.120Fig.3Theexperimentalresultswhenbitrateofdatas′(t)is10.7-Gbit/swithpatternof“10001000”andRFsignalfrequencyis29.425-GHz.(a)OutputsignalwaveformfromIM,(b)and(c)outputsignalwaveformsofMZIfortwosidebandfrequencies,respectively,(d)and(e)detected29.425-GHzOOKmicrowavesignalsatthesupportoftheOTF.(f)thedetectedswithcingmicrowavesignalswithdifferentphase(phasehopping)125Next,weincreasethespeedofswitch,andchangethefrequencyofmicrowavesignalatthesametime.Bysettingthebitrateofdatas′(t)as12-Gbit/swiththesamepatternof“10001000”,andthefrequencyofRFsignalas21-GHz.ThecorrespondingexperimentalresultsareshowninFig.4OneoftheoutputsignalswaveformfromMZIwhenoneopticalsidebandislaunchedasshowninFig.4(a).Thedetected21-GHzOOKmicrowavesignalsareshowninFig.4(b)and(c).130Thegeneratedtwomicrowavesignalwithaπphasedifferenceisswitchedatspeedof83.33-ps,seenFig.4(d).ComparedwithFig.3,wecangetthatwhenthebitrateofdatas′(t)ischanged,theminimumswitchspeedoftwomicrowavesignalsischanged.AndwhenthefrequencyofRFsignalischanged,thefrequencyofgeneratedmicrowavesignalsisalsochanged.-4- 中国科技论文在线http://www.paper.edu.cn135Fig.4Theexperimentalresults:whenthebit-rateofdatas′(t)is12-Gbit/swithafixedpatternof“10001000”andRFsignalfrequencyis21-GHz.(a)DPSKdemodulatedsignalsattheoutputofMZI,(b)and(c)thedetectedOOKmicrowavesignalsusingOTF,(d)thedetectedswithcingmicrowavesignalswithdifferentphase(phasehopping)2ConclusionAfastmicrowavesignalswitchisproposedbasedonthefastswitchoftwocoherentoptical140frequencytones.Inourexperiment,twomicrowavesignalswithapreciseπphasedifferenceareswitchedwithaswitchingspeedofupto83.33-ps.Bysettingthebitofbinarydatas′(t)being“1”or“0”,wecancontroltheswitchofthetwomicrowavesignals.TheswitchingmicrowavesignalsaredecidedbytheinputopticalfrequencytonesandtheirlocationinthetransferfunctionofMZI.Therefore,itcanrealizetheswitchoftwomicrowavesignalswithdifferencephase,ortwo145microwavesignalswithdifferencefrequencyortwomicrowavesignalswithdifferencephaseandfrequency.Thespeedofswitchisindependenttothetypeofswitchingmicrowavesignals.References[1]ArslanH,MahmoudHA,YücekT.OFDMforCognitiveRadio:MeritsandChallenges[J].IEEEWireless150Communications,2009,16(2):6-14.[2]SeedsAJ.MicrowavePhotonics[J].IEEETransactionsonMicrowaveTheory&Techniques,2002,50(3):877-887.[3]KowalczukEK,PanagamuwaCJ,SeagerRD,VardaxoglouJC.Characterisingthelinearityofanopticallycontrolledphotoconductivemicrowaveswitch[A].2010LoughboroughAntennas&PropagationConference[C],155LoughboroughUK,2010.597-600.[4]ZhangF,GeX,PanSL,YaoJP.Photonicgenerationofpulsedmicrowavesignalswithtunablefrequencyandphasebasedonspectral-shapingandfrequency-to-timemappin[J].OpticsLetters,2013,38(20):4256-4259.[5]JiangHY,YanLS,PanY,PanW,LuoB,ZouXH.Microwavephotoniccombfilterwithultra-fasttunability[J].OpticsLetters,2015,40(21):4895-4898.160[6]ShaoY,ChiN,HouC,FangW,ZhangJ,LiX.Anovelreturn-to-zeroFSKformatfor40-Gb/stransmissionsystemapplications[J].JournalofLightwaveTechnology,2010,28(12):1770-1782.[7]ChangQ,TianY,GaoJ,YeT,LiQ,SuY.Generationandtransmissionofopticalcarriersuppressed-opticaldifferential(quadrature)phase-shiftkeying(OCS-OD(Q)PSK)signalsinradiooverfibersystems[J].JournalofLightwaveTechnology,2008,26(15):2611-2618165基于光子技术的高速可调微波开关冯霞，闫连山，姜恒云，盘艳，蒋林，罗斌，潘炜（西南交通大学信息光子与通信研究中心，四川成都610031）170摘要：微波信号开关被广泛应用于雷达、无线以及卫星通信中。与传统的电路控制产生方法相比，基于光学设计产生的微波信号开关具有低损耗、宽带宽以及抗电磁干扰等优点。本文利用马赫曾德尔干涉仪的传输特性和光外差法技术,提出了一种基于光学的高速可调微波信号开关产生方法。方案所得到的微波信号开关具有切换速率高速可调、信号频率和相位可调-5- 中国科技论文在线http://www.paper.edu.cn等特性。并通过实验产生了两组相位差为π，切换速率分别为93.4ps、83.3ps的微波信号175开关，进一步验证了方案的可行性。关键词：微波光子；微波信号开关；相位跳变；马赫增德尔干涉仪中图分类号：O43-6-'