光纤布拉格光栅.ppt

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1、光纖布拉格光柵FiberBraggGratings國立中山大學電機工程研究所林武文教授2006.11.11Ref:AndreasOthonos&KyriacosKalli,FiberBraggGratings,ArtechHouse,Norwood,MA.U.S.A.199927.FiberBraggGratingSensors7.1Introduction7.2SensingExternalFields7.3WavelengthDemodulationofBraggGratingPointSensors7.4SimultaneousMeasurementofTempera

2、tureandStrain7.5PolarizationStabilityofInterrogationSchemes37.FiberBraggGratingSensors7.6MultiplexingTechniques7.7SensorsBasedonChirpedBraggGratings7.8DistinguishingBraggGratingStrainEffects7.9BraggGratingFiberLaserSensors7.10BraggGratingsasInterferometerSensorsandReflectiveMarkers41.1Fibe

3、rBraggGratings7.11OtherBraggSensorTypes7.12ApplicationsofBraggGratingSensors57.1IntroductionFBGissuitableformeasuring-Temperature-strain-pressure67.1IntroductionTheprincipaladvantageisthatthemeasuredinformationis-wavelengthencoded-flexibilitytonetwork-linearity(fromppb~%)-lowinsertionloss&

4、narrowbandwavelength-reflection-easilyembeddedintomaterials77.1IntroductionThekeydetectionissueforFBGis-thedeterminationofsmallmeasurand-inducedwavelengthshifts.CategoryofFBGsensors-pointsensor-array(WDM/TDM/SDM)ordistributed-areflectivemarker(OTDR)-extremelylonggrating87.2SensingExternalF

5、ieldsInch.3welearned(1)Strainresponseofthegratingarisesfromthephysicalelongationofthesensor,leadingtoafractionalchangeinthegratingpitchwithacorrespondingchangeinthefiberindexbecauseofthephotoelasticeffect.97.2SensingExternalFields(2)Thermalresponse-inherentthermalexpansionofthefibermateria

6、l.-thetemperaturedependenceoftherefractiveindex.107.2SensingExternalFieldsEq(3.9)&(3.10)&(3.11)worksformeasuring-acceleration-ultrasonicwaves-forces117.2SensingExternalFields7.2.1PressureSensitivity7.2.2DynamicMagneticFieldSensitivity127.2.1PressureSensitivity(7.1)(7.2a)(7.2b)Apressurechan

7、geofwavelengthshifForSMFWhereEisYoung’smodulus137.2.1PressureSensitivity(7.3a)(7.3b)(7.4)Given,thenormalizedpitchpressureisgivenbyFortherefractive-pressurecoefficientsaregivenbyTherefore147.2.2DynamicMagneticFieldSensitivity(DMFS)Faradayeffect-Alongitudinalmag