Study On Signal Process Technology For Distributed Phase Modulation Fiber Vibration Sensor

While the rapid development of automatic control system in industrial, military and civil fields, sensing technology as the system core obtained wider and wider applications in hu-mankind's daily life. Many new types of sensing devices and methods are developed con-tinuously along with the unceasingly advanced demands for the sensing performance.Fiber sensor, as the sensing element of the sensing application, possessed the outstanding advantages based on its high sensitivity, widely dynamic range and immunity to electro-magnetic interference. In various kinds of fiber sensor including intensity, frequency, wave-length and polarization modulation, the type using phase modulation had the most sensitive.Moreover, the distributed vibration sensor based on phase modulation could achieve con-tinuous and high sensitive detecting and locating of the vibration signals, so it has the broad application prospect. But because of the difficulties in demodulation and location, the signal process of this fiber sensor is always an obstacle resticting its application and development. In this thesis, the signal process of phase modulation fiber sensor was discussed and ana-lysed both in theory and experiments. The main parts are organized as follow:(1) Deduced and analyzed the modulation and demodulation theory of the phase modulation vibration fiber sensor based on studying lots of reference literatures. Then indicate the ne-cessity of demodulation and common demodulation method presently, and discussed the reason why the passive homodyne demodulation was chosen in this experiment.(2) Introduced the basic structure and characteristic of common fiber photoelectric deteting circuit, and described the theoretical model of the PIN photoelectric diode and the choice of applied integrated circuit and the performance of PIN-FET transimpedance preamplifier which used in experiment.(3) Designed the scheme of signal demodulation, and compared the characteristic of 2×2 with 2×3 couplers demodulation method by this experiment. Respectivly introduced and discussed the effects of the phase demodulation methods using the hardware circuit and the LabVIEW software. (4) Analysed the location method of the distributed fiber sensing. Compared the threshold method with the correlation method, then introduced the software correlation location method using high speed data acquisition card and LabVIEW.(5) Investigated the method of establishing joint signal process of distributed fiber sensing and a integral signal process system including spectrum analysis and location in time do-main.Finally drew the conclusion that it can be achieved to resume, analyse and locate the sig-nal from the phase modulation fiber sensor by software method.