Study On Multiplexing Demodulation System Of Fiber Bragg Grating

Fiber Bragg gratings(FBG) used as sensors have been attracted considerable attention due to their high sensitivity, immunity to electric interference, safety and capability of measuring different kinds of physical parameters. Many multiplexing schemes have been proposed based on techniques including wavelength, time, and space division multiplexing to meet multipoint and distributed sensing. Among these techniques, the Wavelength and spatial division combined multiplexing approach has high resolution, but, it is relatively slow. In this paper, a FBG multiplexing demodulation system based on tilted fiber Bragg grating is proposed. The multiplexing technique only demodulates the FBG sensors whose peak wavelength is shifting, so that the demodulation rule is optimized, also the demodulation rate is improved. The primary content includes:Firstly, the analysis methods of fiber grating are introduced, also the simulation of fiber grating using coupled-mode theory and the transfer matrix method is established. The temperature and strain sensing models of FBG are researched, and the commonly FBG demodulation schemes are analyzed. Secondly, the FBG multiplexing demodulation system based on tilted fiber Bragg grating is designed, and the performance and working principle of main devices is analyzed. The characteristics of fiber Fabry-Perot tunable filters are researched, and the comb filter is used to calibrate its nonlinear. Empirical mode decomposition method is proposed to denoise the reflection spectrum of FBG.Finally, transmission wavelength of fiber Fabry-Perot tunable filters as a function of the scanning voltage is obtained though experiment. The filtering effectiveness of EMD is simulated, also through contrast experiment proved the measurement accuracy is improved. The experiments on temperature and strain are done respectively, of which the results show that the experimental data is consistent with theoretical data. Comparing the average delay time of this system with conventional system, the feasibility of the proposed system is well proved.