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班级0901
学生姓名彭博
学号090281
指导教师朱芳
2012年4月
Opticalfibercommunicationtechnology,historyandstatusofdevelopment
Abstract:
Opticalfibercommunicationlinewiththehigh-speed,largecapacity,highsecurity,etc.,butthepracticalapplicationofopticalfibercommunicationscantransmitinformationinthehumanisnoteasy,theirdevelopmenthasexperiencedmanytechnicaldifficultiestosolvethesetechnicalproblems,opticalfibercommunicationscanbefurtherdevelopment.
Thisarticlefromthelightsourceandtransmissionmedium,optoelectronicdevices,opticalfibercommunicationsystemstodemonstratethedevelopmentofopticalcommunicationtechnology.
KeyWords:
OpticalfibercableopticalfibercommunicationtechnologyactivedevicesPassiveComponentsFiberCommunicationSystem
【Body】
Theinherentadvantagesoflightitisdestinedtoserveashumanhistory,therolecannotbeignored,withthedevelopmentofhumantechnology,itsapplicationmorewidely;
theadvantagesarebecomingmoreprominent.
Opticalfibercommunicationistosendtheimage,anddatatotheopticalcarriersignalmodulationtoopticalfiberasthetransmissionmediumofcommunication.Asacarrierwavefrequencyismuchhigherthantheradiofrequencyasthetransmissionmediumoffthancoaxialcableorfiber-opticwaveguidelossismuchlower,sorelativetocablecommunicationsormicrowavecommunications,opticalfibercommunicationhasmanyuniqueadvantages.
Highlighttheadvantagesofrealapplicationsofopticalfibercommunicationstohumanlife,andmanytechnologies,requiresaprocessofdevelopment.
First,theformationofopticalfibercommunicationtechnology
(A),theearlyopticalcommunications
Lighteverywhere,thissentenceisnoexaggeration.Earlyinhumandevelopment,humanbeingshavebeguntouselighttotransmitinformation,andtherearemanysuchexamples.
Gesturesareaformofvisualcommunication,cannotbeinthedark.Thetransmissionsystemduringthedayandthesunaslightsource,solarradiationcarrythesender'
sinformationtransmittedtotherecipient,handmovementsmodulatedlight,thehumaneyeasdetector.
Inaddition,thereisabeacon3000yearsagountilnowstillusethelights,semaphoreandsocanberegardedasprimitiveformsofopticalcommunications.Theemergenceofthetelescopeandgreatlyextendthelightofthesevisualformsofcommunicationdistance.
Suchopticalcommunicationhasasignificantdisadvantageisthattheycantransportcapacityisextremelylimited.
Modernhistory,asearlyas1880,theUnitedStatesBell(Bell)inventedthe"
opticaltelephone."
Thislighttelephoneuseofsunlightorarclampaslightsource,thebeamisfocusedthroughalensinfrontofthevibrationtransmitterlens,sothatthelightintensitychangeswiththevoice,toachievelightintensitymodulatedvoice.Atthereceivingend,withtheparabolicreflectorcameintothebeamreflectedfromtheatmosphereintothesiliconphoto-pool,sothatthelightsignalistransformedintothecurrenttransmittedtothereceiver.
Lightphoneandnotgetinthelivesofactualuse,mainlybecausetherewasnosuitablelightsourceandtransmissionmedium.Theiruseofnaturallightfornon-coherentlight,directionalwell,noteasytomodulationandtransmission;
theairastransmissionmedium,thelosswillbegreat,cannotachievelong-distancetransmission,butalsovulnerabletoweather,trafficandextremelyunstableandreliable.
Itseemsthatthislightthephoneandnotmuchpracticalvalue,however,wehavetosay,lightphoneisstillagreatinvention,itsappearanceasthecarrierprovedthattransmitinformationusinglightwavesispossible,therefore,toBellTelephoneasmodernopticalcommunicationopticalprototypewithouttoomuch.
(B),Theformationofmodernopticalfibercommunicationtechnology
Withthedevelopmentofsociety,increasingtheamountofinformationtransmissionandexchange,thetraditionalmeansofcommunicationcannotmeetpeople'
sneeds.Inordertoexpandthecommunicationcapacity,communicationfromwaveandshortwavedevelopedtomicrowave,millimeterwave,whichisinfactthecarrierfrequencybyincreasingcommunicationthroughcommunicationcapacitytoexpand.
Continuetoimprovethefrequencybandtolight,lightisthemostfamiliarofelectromagneticwaves,thewavelengthatthemicronlevel,andthefrequencyofmagnitudecomparedtoHz,whichhigherthanthecommonlyusedmicrowavefrequency~times.Inviewofthis,usinglightasthecarrierforcommunication,communicationcapacitywillgreatlyexceedthetraditionalmeansofcommunication.
Tothedevelopmentofopticalcommunications,themostimportantissueistofindalightsourceforopticalcommunicationsandtransmissionmedia.
In1970,fiberopticsandlaserresearchatthesametimethetwocomeoutopenedthecurtainofopticalfibercommunication,sowecalledtheOpticalFiberCommunication1970,the"
YearOne."
1,lightsource
In1960,theUnitedStates,Mailman(Thiamin)inventedtherubylaser,whichcanproducecoherentmonochromaticlightthatlightmodulationofhigh-speedinformationaspossible.
Andcomparedtoordinarylight,laserwithnarrowspectralwidth,directionexcellent,highbrightness,andthefrequencyandphasecharacteristicsofamoreconsistentsound.Laserisahighlycoherentlight,itscharacteristicsandradiowavesimilartoanidealopticalcarrier.
However,therubylaserbeamemittedisnoteasytotransfercoupledintothefiber,thecouplingefficiencyisverylow,sotheneedtodevelopminiaturizedlaserlightsources.
In1970,theUnitedStates,BellLabs,NECCorporation(NEC)andtheformerSovietUnionhasbrokenthroughthesemiconductorlaseratlowtemperature(-200)orunderpulsedexcitationconditionsofworkrestrictions,thesuccessfuldevelopmentofroomtemperaturecontinuousoperationofthegalliumaluminumarsenide(Galas)double-heterostructuresemiconductorlaser(shortwavelength).Althoughthelifespanofonlyafewhours,butitsmeaningissignificant,itisthedevelopmentofsemiconductorlaserbasis.In1973,thesemiconductorlaserlifeupto100,000hours(about11.4years),theextrapolatedlifeof100millionhours,fullymeetthepracticalrequirements.Duringthisperiod,1976NTTdevelopedemissionwavelengthof1.3ofindiumgalliumarsenidephosphorus(IngaAsp)laser,in1979theUnitedStatesTelegraphandTelephone(AT&
T)Company,andNTTdevelopedtheemissionwavelengthof155consecutiveoscillationsemiconductorlasers.
Theinventionandapplicationoflaserstomakesleepinga80-yearopticalcommunicationsintoanewstage.
2,thetransmissionmedium
1)Atmospheric
1961to1970,peoplemainlyuseofatmospherictransportofopticalsignals.MassachusettsInstituteofTechnologyuseHe-Nelasersandlasersforatmosphericlasercommunication.Testprovedthatcarryinformationusinglightwavesspreadthroughtheatmospheretoachievepointtopointcommunicationispossible,buttherearemanyatmosphericopticalcommunicationtransmissionseriousproblems:
(1)Communicationcapacityandqualityveryseriouslyaffectedbyclimate.Asrain,fog,snowandatmosphericdustabsorptionandscattering,lightattenuationgreat.Forexample,raincancause30dB/kmattenuation,fogattenuationupto120dB/km.
(2)Thedensityandtemperatureoftheatmosphereisveryuneven,resultinginchangesintherefractiveindex,coupledwiththeimpactofatmosphericturbulence,beampositionshiftmayoccur,andjitter.Thusthedistanceandstabilityofcommunicationareseverelylimited,cannotbeachieved"
allweather"
communication.
(3)Atmospherictransmissionequipmentlocatedataheightrequirement,thesendingandreceivingdevicesmustbeastraightlinevisible.Thegeographicalconditionsmaketheapplicationofatmospherictransportcommunicationhasgreatlimitations.
Althoughsolid-statelasers(forexample,neodymium-dopedyttriumaluminumgarnet(Nd:
YAG)laser)oftheinventionenhancedthelaunchopticalpower,toextendthetransmissiondistance,sothatopticalcommunicationcancrossrivers,islands,andsomespecificoccasionsbetweenuse,buttheatmosphericstabilityandreliabilityoflasercommunicationisstillnotresolved.
Inordertoovercometheimpactofclimateonlasercommunication,peoplenaturallythinkofthelaserbeamislimitedtoaparticularspacetransmission.Haveproposedawaveguidelensandmirrorlightwaveguidetransmissionsystem.Lenswaveguideisametaltubeatregularintervalsfromtheinstallationofalens,eachlensthebeamtransmittedthroughthenextlensconvergenceachieved.Mirrorwaveguideandwaveguidetransmissionsimilartothatusedwiththebeampropagationdirectionattheangleoftwoparallelmirrorsinsteadoflensesandcomposition.
Thetwowaveguidesistheoreticallyfeasible,butinpracticalapplicationsencounteredinsurmountabledifficulties.Firstofall,on-sitecalibrationandinstallationofconstructionisverycomplicated;
secondly,inordertopreventtheimpactofgroundmovementsonthewaveguide,thewaveguidemustbeburiedorselectvehiclesscarceregions.
Intheabsenceoffindingreliableandlow-losstransmissionmedium,opticalcommunication,oncetheresearchintothedownturn.
2)Fiber
Todeveloptheopticalcommunicationtechnology,peoplehaveconsideredandtriedavarietyoftransmissionmedia,includingtheusemadeofglassopticalfibertotransmitlightsignals,butthebestwasthelossofopticalglassmaterialin1000dB/kmabove,suchahightransmissionlosscannotbeuseds