Polarization Interferometric All Opticalfiber Vibration Sensor And Its Application

Fiber optic vibration sensing technology is an active technology in the field of fiber optic sensing,which is widely used in national defense and civil fields such as aerospace,navigation,power and so on.In this thesis,a polarized interferometric all-optical fiber vibration sensing scheme is proposed based on the stress birefringence effect of optical fibers.It has the advantages of simple structure,low cost,fast response,high resolution,scalability and easy maintenance.Firstly,the weak acousto-optic interaction mechanism of optical fibers in the form of perturbation is explored.Based on the coupled mode equation,the mathematical model of weak acousto-optic interaction of bending optical fibers is established.The influence of acousto-optic interaction on the acoustic characteristics and process consistency in the miniaturization design of optical fiber vibration sensor unit is analyzed and simulated.Secondly,a novel polarization interferometric all-optical fiber vibration sensor system architecture is proposed,the coherent detection signal demodulation scheme is adopted to improve the system's response to small disturbances.The dual-path structure is adopted to eliminate the influence of light source fluctuation on the system and improve the sensitivity of the system.In order to further improve the response ability of the system to micro-vibration signals,the system scheme was optimized based on 1/8 wave plate.The mathematical model of the system is established.The influence of phase delay angle and azimuth angle error of 1/8 wave plate on the system measurement accuracy is simulated.The influence of the inherent birefringence of optical fiber on the system sensitivity is analyzed.Then,a prototype of vibration sensor system is designed,and the signal demodulation module is studied.The design methods of light source driving,feedback control,power monitoring and signal acquisition circuit are proposed,and the realization method of signal processing software is explored.According to the requirement of miniaturization design of sensor probe,the selection of sensitive optical fiber is completed,the winding technology of optical fiber ring is optimized,the influence of elastic modulus of sensor sensitizer on the broadband characteristics of system detection is studied,and the acoustic pressure sensitivity of the system is explored.Finally,the experimental prototype of polarization interferometric all-fiber vibration sensor system is developed and the response test of the system to broadband vibration signal is completed.The influence of different filtering and demodulation algorithms on the system test results is studied.The results show that the proposed scheme can effectively detect different frequency vibration signals.