Study Of Sensing Signal Demodulation Technique Based On FBG

Due to all its merit, such as excellent electric insulation, resistance of the interference of electromagnetic, high sensitivity, small volume, light weight, Fiber Bragg grating (FBG) sensor is widely used in architecture, electric power, medicine, chemical engineering. Now, it's becomes one of the most important part of the sensing research, among this the sensing signal demodulation technique is the more important and difficult part, and gets more attention.The subject of this paper is the demodulation experimental research of the FBG sensing signal. We researched much on some demodulation methods, and analyzed the phenomena of the demodulation experiment.Firstly, learned the developing state of the FBG sensing demodulation technique at home and abroad, described it and analyzed the merit and defect of some method.Secondly, the coupled-mode theory of the light transmitting in fiber is expatiated and based on which the Bragg formula and reflectivity/transmission formula is deduced. We also analyzed the sensing principle of FBG strain sensor, press sensor and temperature sensor.The mathematic mode of the matched-filtering dynamic demodulation method is deduced and simulation research is operated. Two demodulation method were experimented, the first is the filtering FBG is controlled by a piezoelectric ceramic (PZT); the second method is that the tunable Fabry-Perot filter is used to demodulate the sensing signal. All the experiment was validate the right of the mathematic mode, and the more important is that we resolved the entire problem in experiment.In the end, the FBG sensing signal demodulation system which controlled by MCS-51 single-chip microcomputer was designed. Two matched-filtering set-ups in the system were deeply analyzed with experiment,the first is the PZT scanning, and the second is the stepping motor scanning. The measure results were displayed by a LED display set-up, and the static sensitivity of 6.7 pm/V and 1 pm/step were obtained.