Distributed Optical Fiber Vibration Sensing System Based On Polarization Analysis

The measurement of the vibration signal plays a crucial role in many important areas, such as structural health monitoring?engineering machinery state analysis?earthquake monitoring,as well as the perimeter security system. Since the optical fiber sensor based on silica fiber has broad application prospects because of passive?distributed and strong ability of anti-interference and adapting to the harsh environment.After the analysis of a variety of optical fiber vibration sensor, this thesis use POTDR(polarized optical domain reflectometry) to study and implement new distributed optical fiber vibration signal sensing system. Traditional POTDR system detects a signal light from the weak Rayleigh scattering of forward propagation light, the SNR of the system is very low. The detection of vibration frequency range is greatly limited because of severalaverage denoising. Meanwhile, a simplified POTDR system can only get the intensity of polarization, is unable to get an accurate frequency and location information of multi-point simultaneous vibration.This thesis first proposes and implements a Fresnel reflection based vibration measurement program, significantly improved signal to noise ratio of the POTDR system by embedding Fresnel reflection point produced by the FC / PC connection the basis of theoretical analysis. Without any average denoising, it can detect and locate the vibration signal. The technology overcomes the adverse effects of depolarization effect on the measurement dynamic range of the traditional OTDR systems, increasing the measuring range of the vibration frequency, achieving a quasi-distributed high-precision measurement of vibration signals. Then, we proposed and implemented multipoint vibration measurement methods based on the spectrum linear moving technology, separated the vibration signal from different area in order to determine the vibration signal of the same frequency in two different locations, realizing the localization and frequency of events measurement at the same time. Through this thesis work, I build a complete hardware system and software control and data processing platform of distributed optical fiber vibration sensing system base on POTDR technology, laying a solid foundation for engineering practice of distributed optical fiber vibration measurement technology.