Research On Distributed Feedback Fiber Optic Temperature Sensor

Distributed optical fiber temperature sensor has many advantages compared with traditional sensors: integration of sense and transmission,remote measurement and monitoring;the temperature distribution can be obtained over the whole fiber by measuring once only,The information of unit cost is reduced significantly because of hundreds of thousands of pieces of information can be got in a kilometers of loop of the sensor optical fiber;wide measurement range,high spatial resolution and high accuracy;distributed fiber-optic temperature sensor has many incomparable advantages under the harsh environment,for example environment with strong electromagnetic interference or inflammable and explosive and other sensors can not be closed.Therefore,people have carried out a wide range of research on distributed optical fiber temperature sensors since 1980 s.In this paper,a folding structure distributed fiber optic sensor based on Raman scattering and a chirped grating sensor are designed,which can be used to monitor the different temperature fields in order to prevent the occurrence of fire.The research contents are as follows:Firstly,the traditional distributed optical fiber temperature sensor(Stokes and anti-Stokes dual channel demodulation method based on Raman scattering)exist some problems,this paper proposes a folding structure distributed optical fiber temperature sensor and the demodulation method using anti-Stokes only.The optical fiber temperature sensor with folding light path is designed,and complete temperature demodulation method based on anti-Stokes is put forward according to its working principle,the signal is processed by the cumulative average and wavelet transform.Finally,the measurement error within1.7?.In order to solve the problem of low resolution of traditional distributed temperature sensor,a temperature measurement method based on linear chirped grating interferometric temperature sensor is proposed.The variation of the Prague wavelength of the grating is correlated with the temperature,but the wavelength change is small through analysis of the characteristics of the chirped grating.This method is realized by detecting of interference beat frequency changes with the temperature.The interference beat is generated by feedback light of the reference grating and the grating sensor,finally the temperature sensitivity is 22.5THz/?.