Research Of Key Problems In Fiber Optic Sensing System

This dissertation aims at the key technologies in FOSS for seismic signals. With the rapid development of information technology, Fiber Optic Sensing System (FOSS) has found a number of applications in civil engineering, mechanical engineering, military and so on. One of the important applications of FOSS is the fiber optic accelerometer which is used to detect the seismic signals caused by moving targets on earth. The signals collected by the accelerometer are transmitted to the recognition unit and classified according to different targets subsequently. The optical fiber accelerometer has many advantages over traditional sensors such as high sensitivity, immunity to electromagnetism interference (EMI) and wide dynamic range.First, in this paper, the status of Unattended Ground Sensor (UGS) is reviewed. Based on the theory of fiber optic interferometry, the scheme of FOSS is introduced. Second, the key technology of laser source is studied. A power source is designed for laser diode and a C band multi-wavelength laser source is developed for wavelength division multiplexing. Third, some seismic signals collected by a fiber optic sensing system are analyzed in time and frequency domain. The seismic signal was processed by down-sampling and noise reduction, and the eigenvector was extracted with the wavelet packet. Considering decomposition scale and sample numbers, an appropriate signal analysis method for the FOSS was presented. Also, the eigenvector was evaluated. At last, the results of test in the outfield are introduced.The mostly points of this dissertation are as follows:Put out and realize the theory on which the fiber optic sensing system basesPlan and implementation multi-wavelength laser sourceProcess seismic signals in FOSSIntroduce the results of test in the outfield...