Research On Multiplexing And Demodulation Technique Of Fiber Grating Sensor Based On Genetic Algorithm

Nowadays, among different optical fiber grating sensor techniques, FBG(Fiber Bragg Grating)sensor is one of the most popular researched technique. FBG measurement is not affected by the light source disturbance, electromagnetic signals and so on, so FBG sensor has been widely used in many fields. Because of its wavelength-encode characteristics, how to accurately measure the small shift of Bragg wavelength become one of the main bottleneck of the research on the FBG sensor.The principle of FBG sensor , some methods of demodulation and multiplexing technique and genetic algorithm are introduced in the thesis. After analyzing the advantages and disadvantages of various demoudulation methods and multiplexing technique, one demodulation method that based on F-P tunable filter and spectral shape multiplexing, using genetic algorithm is presented. The theoretical feasibility of the demodulation method is verified both by the theory and MATLAB simulation.According to the actual situation and specific algorithm requirement, DSP chip (TMS320VC5416) and the peripheral circuits have been designed to make hardward circuit board. The core algorithm and the control software are programmed by using C language. The PC interface is programmed by using VC.Using simulated signal data, the presented algorithm is activated on the hardware circuit board. The results show that genetic algorithm can demodulate the Bragg wavelengths by using proper parameters even when the spectrum of one FBG overlaps with others'. Therefore, the method can save spectral bandwidth and increase the number of multiplexed gratings effectively.