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基于正交偏振控制的布里渊光时域分析长距离分布式光纤传感器.docx

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基于正交偏振控制的布里渊光时域分析长距离分布式光纤传感器 Introduction Fiberopticsensorshavebeenfoundtohavenumerousapplicationsoverthepastfewdecadesduetotheirinherentadvantagessuchashighsensitivity,immunitytoelectromagneticinterference,andeaseofinstallation.Amongthese,distributedfiberopticsensorsareemergingasanewclassofmonitoringsystemsthatenablemeasurementofphysicalparameterssuchastemperature,strain,andpressureoverlongdistances.Thebasicprincipleofdistributedsensingisbasedonmonitoringthechangesinpropertiesoflightthatpropagatesalongtheopticalfiber.OneofthemostwidelyusedtechniquesfordistributedsensingisbasedontheinteractionbetweenlightandtheacousticwavethroughthephenomenonknownasBrillouinscattering. ThispaperdiscussesanovelapproachtoimprovetheperformanceofdistributedfiberopticsensorsbasedonBrillouinscatteringbyusingorthogonalpolarizationcontrol.Theproposedtechniqueisbeneficialinthatitenablesthemeasurementofbothtemperatureandstrainwithhighspatialandtemporalresolutionoveralongdistanceandwithhighsensitivity. PrincipleofBrillouinScattering Brillouinscatteringisaphenomenoninwhichtheinteractionoflightwithanacousticwaveinfiberopticleadstothegenerationofascatteredlightwavewithdifferentpropertiesthantheincidentlightwave.Theinteractionoflightandacousticwavesisduetotheelectrostrictionandphotoelasticeffects,respectively.Whenanopticalpulseispropagatingthroughthefiber,itgeneratesatime-dependentacousticperturbationinthefiber.TheinteractionbetweentheacousticwaveandtheopticalpulseresultsinashiftoftheopticalfrequencywhichisknownastheBrillouinfrequencyshift(BFS).TheBFSisproportionaltotheacousticvelocity,andhencetothelocalvaluesoftemperatureandstraininthefiber. OrthogonalPolarizationControl Theproposedtechniqueisbasedontheuseoftwosetsoflaserpulsesthatarelinearlypolarizedinorthogonaldirectionstoexcitebothacousticmodesinthefiber.ThisapproachisbeneficialinthatiteliminatestheeffectofpolarizationdependentBrillouinscatteringwhichisasourceoferrorinconventionalBrillouinsensing.Thetwosetsoflaserpulsesarealternatedatahighfreq