光纤光学英文文献1资料下载.pdf

光纤光学英文文献1资料下载.pdf

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SensorsandActuatorsA112（2004）308312Asimplefiber-opticcurrentsensorusingalong-periodfibergratinginscribedonapolarization-maintainingfiberasasensordemodulatorYongWookLee,IlyongYoon,ByounghoLeeSchoolofElectricalEngineering,SeoulNationalUniversity,Kwanak-GuShinlim-Dong,Seoul151-744,SouthKoreaReceived19September2002;@#@receivedinrevisedform5December2003;@#@accepted12January2004AbstractWeproposeasimplefiber-opticcurrentsensorbasedontheFaradayrotationeffect,whichfirstlyutilizesafiber-compatiblepolarizationanalyzerasasensordemodulator.Thefiberpolarizationanalyzer（demodulator）wasfabricatedbyinscribingalong-periodfibergratingonapolarization-maintainingfiber.Themanufacturedfiberpolarizationanalyzerhasthepolarizationextinctionratioofmorethan25dBatthefixedwavelengthof1522.5nm.Currentsensingupto600Armswasdemonstratedinasimpleandcost-effectiveway,showingagoodlinearity.2004ElsevierB.V.Allrightsreserved.Keywords:

@#@Opticalfibersensor;@#@Currentsensor;@#@Polarization-maintainingfiber;@#@Long-periodfibergrating1.IntroductionSincetheearlydemonstrationsoftheprincipleofopti-calfibercurrentmonitoringbySmith1,aconsiderableamountofresearchefforthasbeenexpendedforthedevel-opmentoffibercurrent-measurementsensors26.Untiltoday,agreatmanycurrentsensingsystems,whichareincorporatingflintglassopticalfibers7,aSagnacinter-ferometerstructure811,andothertechniques12,13,havebeenreported.Thefiber-opticcurrentsensorconsistsofacoiloffiberwoundaroundtheconductorcarryingacurrent,alightsource,andapolarizationanalyzer.TheFaradayrotationeffectcausesarotationoftheplaneofpo-larizationofthelightpropagatinginthefiberinproportiontothecurrentflow.Henceademodulationoftheelectriccurrentcanbeperformedbyanalyzingtheoutputplaneofpolarization.Inthispaperweproposeasimplefiber-opticcurrentsensorbasedontheFaradayrotationeffect,whichfirstlyutilizesafiber-compatiblepolarizationanalyzerasthesensordemodulator.Thefiberpolarizationanalyzerwasfabricatedbyinscribingalong-periodfibergrating（LPG）onapolarization-maintainingfiber（PMF）.Themanufac-tureddevice（polarization-maintaining-LPG:

@#@PM-LPG）hasthecharacteristicsofafiberpolarizationanalyzer（polarizer）atacertainfixedwavelengthduetothebirefringenceofCorrespondingauthor.Tel.:

@#@+82-2-880-7245;@#@fax:

@#@+82-2-873-9953.E-mailaddress:

@#@byounghosnu.ac.kr（B.Lee）.thePMFandtheco-directionalmodecouplingoftheLPG1416.Intheconventionalfiber-opticcurrentsensor,thepolarizationanalyzerconsistsofafewbulk-opticcompo-nents.Especially,inthefabricationprocessofthebulk-typepolarizationanalyzer,opticalcomponentslikecollimatingandfocusinglensmustbepreciselyalignedtoreducethecouplinglosswiththeopticalfiber.Intheproposedcurrentsensor,however,thePM-LPGdoesnotrequireanybulk-typecouplingcomponentsandprecisealignmentoftheseopticalcomponentswiththeopticalfibertoreducethecou-plingloss.Thustheproductioncostofthecurrentsensorsystemcanbelowerbyreplacingconventionalpolarizationanalyzerwiththeproposedfiberpolarizationanalyzer.Inconsequence,currentsensingupto600Arms（root-mean-square）wasdemonstratedinasimpleandcost-effectiveway,showingagoodlinearity.2.TheoryBeforewebegintoexplaintheoperatingprincipleoftheproposedsensor,wearegoingtosimplyexaminethespec-tralcharacteristicsofthePM-LPG.Theresonantwavelength0intheco-directionalmodecouplingbetweenthefunda-mentalcoremodeandtheleakycladdingmodesintheLPG,canbeobtainedthroughthefollowingequation:

@#@0=ncoreeffncladeff

（1）0924-4247/$seefrontmatter2004ElsevierB.V.Allrightsreserved.doi:

@#@10.1016/j.sna.2004.01.041Y.W.Leeetal./SensorsandActuatorsA112（2004）308312309wherencoreeffandncladeffaretheeffectiverefractiveindexofcoreandcladdingmodes,respectively,andisagratingpitch.InthecaseofaPMF,theasymmetryofthewaveguidestructureintroducessomedifferencebetweentherefractiveindicesoftwolinearlypolarizedmodespropagatingthroughthecoreandcladding.Itmeansthatwavelengthsforwhichcouplingcondition

（1）issatisfiedaredifferentdependingonthestateofpolarization（SOP）.Thisresultsinasplittingofthelossbands.Inthiscaseonlyonelinearlypolarizedmodecanbesuppressedatafixedwavelength14,15.Now,inthefiber-opticcurrentsensor,theazimuthalangleoftheinputpolarizationrotatesinproportiontotheappliedcurrentduetotheFaradayrotationeffect.TheFaradayro-tationofalinearlypolarizedlightinthepresenceofamag-neticfield,whichcanberegardedasmagneticallyinducedcircularbirefringence,canberepresentedas（ignoringthelinearbirefringenceeffect）（,T）=V（,T）?

@#@Hd?

@#@l

（2）whereistheangleofrotationofthepolarizationplane,thefreespacewavelengthoflight,Ttheambienttemperatureofth