Research On Key Technology Of Temperature And Strain Sensing System Based On Coherent BOTDR

The characteristics and the sensing mechanism of temperature and strain of Brillouin scattering in optical fiber have been analyzed, and the temperature and strain dependences of Brillouin spectrum have been deduced. The method to use FFT to get temperature and strain information directly over wideband in BOTDR system has been simulated by Matlab. The principle using nonlinear mirror structure to improve the signal-to-noise ratio of BOTDR system has been analyzed, and its application arrangement in direct detection and coherent detection BOTDR sensing system has been proposed. A simultaneous measurement system of temperature and strain based on Landau-Placzek Ratio, using coherent detection of Brillouin scattering, has been presented. The design ideas of optical source subsystem, pulse modulation subsystem, microwave down converter subsystem and so on, have been discribed in detail with emphasis on the microwave down converter subsystem. The design considerations and parameters of each component in microwavc down converter subsystem have been given. Finally, the experimental study of transmitted light and backscattered light signal has been conducted.