Research and Theoretical Analysis of New Fiber Bragg Grating sensor demodulation system

ABSTRACT In order to measure high-precision and large scale sensing signal and solve two-values question in signal detecting of strain sensor ,we design a new kind of FBG matching demodulation system based on fiber Bragg grating matching demodulation principle. Through paralleling connection two gr oups of grating-matching whose center wavelength equal to sensing grating’s, and then analyzin g reflectance spectrum, we could get the relationship of strain and optical power detected by photoelectric detector. Then we can set up the theoretical model and complete system simulation. The simulation results show that the scheme is feasible. The scheme not only can solve the problem of double values and can simultaneously detect the positive and negative strain. The sensor measurement range can be up to 952 PH. Key words: Sensor technology; Fiber Bragg Grating; Matching demodulation; Two-values 1. INTRODUCTION Fiber Bragg gratings are attracting considerable interest for application as sensors, because of its’ inherent wavelength-encoded characteristics. Wavelength-encoded signal demodulation is one of the key techniques for the Fiber Bragg grating sensing systems to enter into a practicable step. Having developed a high sensitivity, wide measurement range, fast and accurate wavelength-coded signal demodulated FB G sensor system is a realiza tion of optical fiber grating sensor in terms of engineering application. There are several mature demodulation techniques in the fiber Bragg grating sensing demodulation filed. For example, Spectrometer, Monochrometer, Filtering demodulation method, Interference demodulation method, Chirp grating method, Tunable narrow-band light scanning demodulation method. Most of these mature demodulation technique have some drawbacks. Spectrometer and monochrometer belong to lager, cumbersome and more expensive devices, cannot be applied to real-time projects. Filteri ng demodulation method and Inte rference demodulation method have a low resolution ratio and narrow measurement range