Study On Sensing Signal Demodulation Technique For Fiber Bragg Grating

Fiber Bragg grating (FBG) sensor is one of the current heat researchfields in the optical fiber grating sensor technique fields. It is widely applied inmany fields such as the structure monitoring of the large compound materialand the concrete, the performance monitoring of the intelligent materials,electric power industry, medicine, chemical engineering etc. The demodulationtechnique of the FBG is currently a critical and difficult problem in nowadaysFBG censoring technique fields.Based on analysis of domestic and foreign study actualities on FBG anddemodulation technique for FBG, a new demodulation technique for FBG ispresented. The main content of the dissertation is:The coupled-mode equations of fiber Bragg gratings are expatiated andtransform matrix analyzing method of FBG is studied;the Bragg condition offiber Bragg grating and biggest reflectance formula are presented. Based onanalysis of Sensing principle of fiber Bragg grating, strain sensing model andtemperature sensing model are created.On the basis of analyzing and researching principle of demodulationtechnique for FBG, a scheme of demodulation technique for FBG which isbased on stepping motor controlling cantilever tuning is presented. Thecantilever is systemically designed.A scheme of demodulation technique for FBG which is based oncantilever tuning and the demodulation technique on a pair of matched FBGs isdesigned. The relation between the wavelength shifts of sensing FBG and thewavelength shifts of reference FBG is studied. The relation between reflectedpower of FBG and the figure of spectrogram is created.The measuring circuit of reflected power, controlling circuit of steppingmotor and the signal processing system based on single-chip microcomputerare designed.Using the sensing signal demodulation technique for FBG which isdesigned, the experiments for testing the temperature and strain responseproperties of FBG is made. Using the isosceles triangle cantilever, referenceFBG is tuned. Sensing signal demodulation for FBGs is realized. Thefeasibility of this demodulation scheme is conformed.