Introduction
Anopticaldevicethatrealizesthedistributionorcombinationofopticalsignalpoweramongdifferentopticalfibers.Itisconstitutedbythemutualexchangeofguidedwaveenergyindifferentfiberfacesadjacenttothefibercorearea.Accordingtothetypeoffiberused,itcanbedividedintomultimodefiber,singlemodefiberandpolarizationmaintainingfibercoupler.
Opticalfibercoupler(Coupler),alsoknownassplitter(Splitter),connector,adapter,flange,isusedtorealizeopticalsignalsplitting/combining,
moduleOpticalfibercoupler(3photos)
Orcomponentsusedtoextendopticalfiberlinks,belongtothefieldofopticalpassivecomponents,andareusedintelecommunicationsnetworks,cableTVnetworks,userloopsystems,andlocalareanetworks.Willbeappliedto.Opticalfibercouplerscanbedividedintostandardcouplers(belongingtowaveguidetype,doublebranch,unit1×2,thatis,theopticalsignalisdividedintotwopowers),direct-connectcoupler(connectingtwoopticalfibersofthesameordifferenttypesofopticalfiberinterfaces,withExtendtheopticalfiberlink),star/treecoupler,andwavelengthmultiplexer(WDM,ifthewavelengthishigh-densityseparation,thatis,thewavelengthspacingisnarrow,itbelongstoDWDM),theproductionmethodsincludesintering(Fuse),microTherearethreetypes:MicroOpticsandWaveGuide.Thesinteredmethodaccountsforthemajority(about90%).Themanufacturingmethodofsinteringmethodistomeltandstretchtwoopticalfiberstogethertopolymerizethecorestogethertoachieveopticalcoupling.Themostimportantproductionequipmentistheopticalfiberfusionsplicer,whichisalsoanimportantstep.Someimportantstepscanbemanufacturedbymachines,butaftersintering,peoplestillneedtoworktoinspectandpackage,solaborcostsabout10-15%,andtheuseofmanualinspectionandpackagingmustensuretheconsistencyofquality,whichisalsothereasonformassproduction.Itmustbeovercome,butthetechnicaldifficultyisnotashighasthatofDWDMmodulesandopticalactivecomponents.Therefore,mostofthemanufacturerswhowanttoentertheopticalfiberindustryattheinitialstagewillstartwithopticalcouplers,andthegrossprofitwillbe20-30%.
Principle
Theopticalfibercouplerisadetachable(movable)connectiondevicebetweentheopticalfiberandtheopticalfiber.ItpreciselyconnectsthetwoendfacesoftheopticalfibertomakethelaunchingfiberTheoutputlightenergycanbecoupledtothereceivingfibertothemaximumextent,anditcaninterveneintheopticallinktominimizetheimpactonthesystem.Forthewaveguidefibercoupler,itisgenerallyaY-branchelement,andtheopticalsignalinputbyanopticalfibercanbedividedequallybyit.Whentheopeningangleofthebranchofthecouplerincreases,theamountoflightleakingintothecladdingwillincreasetoincreasetheexcessloss.Therefore,theopeningangleisgenerallywithin30°,sothelengthofthewaveguidefibercouplercannotbetooshort.
Single-modefibercoupler
Single-modefibercoupleristhemostwidelyused.The2×2single-modefibercoupleristypical,anditscompositionisshowninthefigure.Ithastwoinputterminalsandtwooutput
terminals,withacouplingareainthemiddle.Figure2(a)ismadebythemelt-stretchingprocess.Thestretchedpartformsataperedcouplingzone.Stretchingmakesthelightenergyofthecoreareaexpandoutofthecore;atthesametime,bringingthetwocoresclosetoeachother,bothofwhichenhancethecoupling.Theopticalsignalinputby1or2isdistributedthroughthetaperedcouplingareaandoutputbythe3and4terminals.Thedistributionratioiscalledthecouplingratio,whichiscontrolledbythelengthofthestretchingzone.Inthefigure(b),partofthecladdingisremovedfromtheopticalfiberembeddedinthequartzblockwithacertaincurvaturebythegrindingandpolishingmethod,andthentwosuchquartzblocksarepressedtightlytomakethetwocoresclosetoeachothertoformanopticalfibercoupler.Thecouplingratioisdeterminedbytheproximityofthecoreandtheradiusofcurvatureofthefiberinthequartzblock.Thecouplingratiocanbeselectedfrom1%to99%,andtheinsertionlossislessthan0.5dB.Theopticalsignalcoupledoutoftheinputlightintheoppositedirectionisextremelyweak,sothefibercouplerisoftencalledadirectionalcoupler.
Multimodefibercoupler
Theprincipleandstructureofthemultimodefibercouplerarebasicallysimilartotheabove,exceptthatthegrindingandpolishingdevicerequiresstrongcoupling,sothegrindingandpolishingplaneentersthefiber.core.Onthebasisofthepolished2×2fibercoupler,anadjustablecouplercanalsobemade.Inthecaseofacertainwavelength,thecouplingratiochangeswiththeangleformedbythetwopolishedfibers,sothecouplingratiocanbechangedbyadjustingtherelativedirectionofthetwofibers.
Inopticallocalnetworksorotheroccasions,l×N,N×1couplersorN×Mcouplers(orstarcouplers)arealsoused.Thefirstnumberrepresentsthenumberofinputterminals,andthefirstThetwonumbersrepresentthenumberofoutputterminals.Thesecouplersaremadebyfusiondrawingmethod.
Classification
Accordingtothedifferentopticalfibercoupling,therearethefollowingclassifications:
SCopticalfibercoupler:appliedtoSCopticalfiberinterface,itcanbeseenwithRJ-45interfaceItlooksverysimilar,buttheSCinterfaceisflatter.Theobviousdifferenceisthecontactsinside.Ifitis8thincoppercontacts,itisanRJ-45interface.Ifitisacopperpillar,itisanSCfiberinterface.
LCopticalfibercoupler:ItisusedinLCopticalfiberinterfacetoconnecttheconnectorofSFPmodule.Itismadeofeasy-to-operatemodularjack(RJ)latchmechanism.(Commonlyusedinrouters)
FCopticalfibercoupler:usedinFCopticalfiberinterface,theexternalstrengtheningmethodisametalsleeve,andthefasteningmethodisaturnbuckle.GenerallyusedontheODFside(mostusedonthedistributionframe)
STfibercoupler:usedinSTfiberinterface,oftenusedinfiberdistributionframes,theshellisround,andthefasteningmethodisturnbuckles.(For10Base-Fconnection,theconnectorisusuallySTtype.Oftenusedinopticalfiberdistributionframe)