A novel method of elimination of light polarization cross sensitivity on tilted fiber Bragg grating bending sensor

Abstract

ThearticleshowsthepossibilityofusingTFBGgratingstomeasuretheradiusofcurvatureoffiberbendinginconditionsofvariablepolarizationoftheintroducedlight.Mostofthemodern,stablelightsourcesgenerate lightwithahighdegreeofpolarization.Duetothespatialasymmetry,thedirectionofthelightpolarization planeaffectsthespectralparametersofindividualmodes.Forthisreason,inthemeasurementsystemsusing TFBGspresentedsofaritbecomesnecessarytodetermineandcontrolthestateoflightpolarizationdirectly infrontoftheperiodicstructure.Thearticlepresentsthedeterminedspectralparametersofthecladding modeswhichallowbendingmeasurementsregardlessofthedirectionofpolarizationoftheintroduced light.Thankstothis,themeasuringsystemcanbeconstructedwithoutprovidingcontroloftheintroduced lightpolarizationangle,whichmakesitsconstructionsimpler.WhenusingTFBGswithanangleof2 ◦ , the accuracy of determining the bending radius in the range from 15 mm to 30 mm when changing the angle of the plane of polarization in the full range is 0.318 mm in the case of changes in the transmission coefficient. For changes in the wavelength of the selected cladding mode, the accuracy is 0.3203 mm, with the input light polarization being changed in the range from 0 ◦ (P type) to 90 ◦ (S type).