Theoretical And Experimental Study Of The BOTDA Based Temperature / Strain Sensing Technology

In this thesis, the principle of Brillouin scattering has been introduced with particular attention to the basic theory of stimulated Brillouin scattering, and the characteristics of the Brillouin spectrum has been analyzed. According to SBS frequency shift was affected by temperature and strain, a function between SBS frequency and temperature or strain had been established, which based on SBS frequency shift affected by temperature and strain. Pre-pump pulse Brillouin optical time-domain analysis principle was further studied based on the analysis of light leakage in BOTDA system. The theoretical model of the PPP-BOTDA based on perturbation solution was studied, and established stability theoretical foundation for continue study of PPP-BOTDA system. The principle and the working point drift characteristics of Electro-optic modulator have been studied, and the appropriate bias voltage control module was selected. Meanwhile the bias voltage control experiment of BOTDA sensing system was designed according to its features and functions. The purpose of this experiment was used to verify the performance of bias voltage controller in terms of eliminating the transmission curve drift of Electro-optic modulator EOM, in order to obtain the stable sensing pulse.The principle and function of polarization control were studied in detail, and the polarization control experiment of the input light was designed based on EOM. The polarization control program was written. The experiment of fixing the linearity of output voltage has been done, and the experimental results were simulated and analyzed. The input and output voltage's correction of polarization control module was achieved. The measurement experiment of half-wave voltage of polarization control module was completed, and the experimental data was analyzed by using extreme value method, and the half-wave voltage of Channel 1 and Channel 2 were obtained. The experiment system of polarization control unit has been built, and the performance of polarization control system was studied by the experiment. The results show that the dynamic polarization control can be achieved basically.