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RF和微波光纤设计指引Name:Class:StudentNO.:1RFandMicrowaveFiber-OpticDesignGuideAgereSystemsInc.,throughitspredecessors,begandevelopingandproducinglasersanddetectorsforlinearfiber-opticlinksnearlytwodecadesago.Overtime,theseoptoelectroniccomponentshavebeencontinuallyrefinedforintegrationintoavarietyofsystemsthatrequirehighfidelity,highfrequency,orlong-distancetransportationofanaloganddigitalsignals.Asaresultofthiswidespreaduseanddevelopment,bythelate1980s,theselinkproductswereroutinelybeingtreatedasstandardRFandmicrowavecomponentsinmanydifferentapplications.Thereareseveralnotableadvantagesoffiberopticsthathaveledtoitsincreasinguse.Themostimmediatebenefitoffiberopticsisitslowloss.Withlessthan0.4dB/kmofopticalattenuation,fiber-opticlinkssendsignalstensofkilometersandstillmaintainnearlytheoriginalqualityoftheinput.Thelowfiberlossisalsoindependentoffrequencyformostpracticalsystems.Withlaseranddetectorspeedsupto18GHz,linkscansendhigh-frequencysignalsintheiroriginalformwithouttheneedtodownconvertordigitizethemforthetransmissionportionofasystem.Asaresult,signalconversionequipmentcanbeplacedinconvenientlocationsoreveneliminatedaltogether,whichoftenleadstosignificantcostandmaintenancesavings.Savingsarealsorealizedduetothemechanicalflexibilityandlightweightfiber-opticcable,approximately1/25theweightofwaveguideand1/10thatofcoax.Manytransmissionlinescanbefedthroughsmallconduits,allowingforhighsignalrateswithoutinvestinginexpensivearchitecturalsupports.Theplacementoffibercableisfurthersimplifiedbythenaturalimmunityofopticalfibertoelectromagneticinterference(EMI).Notonlycanlargenumbersoffibersbetightlybundledwithpowercables,theyalsoprovideauniquelysecureandelectricallyisolatedtransmissionpath.Thegeneraladvantagesoffiber-opticsfirstledtotheirwidespreaduseinlong-hauldigitaltelecommunications.Inthemostbasicformoffiber-opticcommunications,lightfromasemiconductorlaserorLEDisswitchedonandofftosenddigitallycodedinformationthroughafibertoaphotodiodereceiver.Bycomparison,inlinearfiber-opticsystemsdevelopedbyLucent,thelightsentthroughthefiberhasanintensitydirectlyrelatedtotheinputelectricalcurrent.Whilethisplacesextrarequirementsonthequalityofthelasersandphotodiodes,ithasbeenessentialinmanyapplicationstotransmitarbitraryRFandmicrowavesignals.Asaresult,tensofthousandsofAgereSystems’transmittersarecurrentlyinuse.Theinformationofferedhereexaminesthebasiclinkcomponents,providesanoverviewofdesigncalculationsrelatedtogain,bandwidth,noise,anddynamicrange2anddistortion.Asectiononfiber-opticcomponentsdiscussesanumberofkeyparameters,amongthemwavelengthandloss,dispersion,reflections,andpolarizationandattenuation.Additionalinformationevaluatesopticalisolators,distributed-feedbacklasersandFabry-Perotlasers,predistortion,andshort-vs.long-wavelengthtransmission.OneoflinearopticalfiberrelationmainusagesorreceivesbetweentheelectronicinstallationandtheremotelocalizationantennainthetransmissiontransmitsRFandthemicrowavesignal。Becauseoftheopticalfiberchainflexibility，possiblycanforthesimulationordigitalsignaldesignsomeantennas，includingthemilitaryandthecommercialcommunicationssatellite，thegloballocalizationsatellite，theremotesensingwithtracesthelighthouse，orwirelesscellnetwork。Anotherkindoftypechainistheopticalfiberdelayline，installsinapackageitincludingatransmitter，areceiver，withlongtextilefiber。Itmayprovidethelongdelaytime,highbandwidth,withlowweight.Thesehigh-frequencyRFandthemicrowaveproducthasobtainedbenefitsfromtheuselinearopticalfiberequipmentcabletelevisionragingtidemiddleearth.Inhere,thetextilefiberexpandstheTVsignalthetransmittingrange,improvestheirqualityandthesystemreliability,butwhenmerelyonlyhastheelectriccable,evenwiththesystemwhichusedcompareshassavedtheexpenseIneachoftheseapplications,aswellasmanyothers,theAgereSystems’transmittersandreceiverscomprisingthelinksaresimilarandcanbetreatedasstandardmicrowavecomponents.Focusingonthesecommonelements,thisdesignguidedescribesthegeneraltechnicalconsiderationsandequationsnecessaryforengineerstochoosethemostappropriateAgereSystems’componentsfortheirsystems.Theseequationsalsohavebeenincorporatedintovariousprograms,whichanAgereSystems’applicationsengineercanusetoprovideananalysisforaspecificlinkapplication.Figure1showsthethreeprimarycomponentsinafiber-opticlink:anopticaltransmitter,afiber-opticcable,andanopticalreceiver.Inthetransmitter,theinputsignalmodulatesthelightoutputfromasemiconductorlaserdiode,whichisthenfocussedintoafiber-opticcable.Thisfibercarriesthemodulatedopticalsignaltothereceiver,whichthenreconvertstheopticalsignalbacktotheoriginalelectricalRFsignal.3RF和微波光纤设计指引大概二十年以前，Agere系统公司通过其前辈开始发展和生产激光和检测器线性光纤的联系。这些电子元件组成部分连续不断地为了进入各种各样要求高保真，高频率，或者长途模拟和数字的信号的运输的系统。由于这广泛传播的使用和发展，八十年代末，这些系列产品通常被认为是标准的RF和微波组成部分不同的应用。光纤的许多引人注意的优势使它被越来越广泛的应用。光纤设备的最主要的好处是其损失低。由于光的减弱的小于0.4dB每公里，光纤传送的信号几乎可以传输数十公里并且仍然保持原来的输入的质量。对于最实际的系统低的纤维损失也是独立的频率。用激光和检测器加速到18GHz，联系能以他们原来的形式发送高频信号，无须改变或者为了一个系统的传输部分使他们数字化。因此，信号转化设备便可以闲置或者干脆不用，这样便可以节省一部分费用。机械的灵活性节省了费用，同时，轻量级光纤电缆，大约只有1/25波导的重量的1/10coax。考虑到高的信号速率没有昂贵的建筑投资方面的支持。许多传播线能通过小的导管支持。光缆