Research On Sensing Properties Of W-type Optical Fiber Bragg Grating

Fiber Bragg grating(FBG)is one of the most rapidly developing optical fiber passive devices in recent years.FBGs exhibit several advantages including low price,strong stability,small size,anti-electromagnetic interference and corrosion resistance and have been widely developed as a sensing device in recent years.Either the center-wavelength or the intensity of the reflection spectrum of the FBG inscribed in a W-type fiber can be used as a sensing element.Research on basic sensing characteristics of W-type fiber Bragg grating in temperature sensing,strain sensing,refractive index sensing and other aspects will further help to find the advantages of W-type fiber Bragg grating in sensing field and extend its application.First of all,based on Coupled-Mode Theory(CMT)and analysis of mode of W-type fiber,we analyzed theoretically the coupled mode of W-type fiber Bragg grating.And combining with Mode Solution and Matlab,we simulated the reflection spectrum of W-type fiber Bragg grating.Then we analyzed about in detail and simulated axial strain,temperature and refractive index sensitivity of W-type fiber Bragg grating.Besides,we set up an experimental platform to study the sensing characteristics of temperature,strain and refractive index of W-type fiber Bragg grating.At the end,we proposed temperature-insensitive refractive index sensing and temperature-insensitive strain sensing based on the intensity of reflective resonant peaks.