Research And Realization On Key Technologies Of Portable Optical Fiber Vibration Sensing System

Optical fiber sensing technology is a kind of sensing technology measuring a widevariety of physical quantities based on the optical properties of optical fiber, which has manycharacteristics, including high sensitivity, strong anti-electromagnetic interference capability,fast response and long service life. Distributed fiber sensing technology even makes full useof the axial property of optical fiber to sense the environment parameters along the wholefiber, which makes this technology possess some more advantages such as easy network ing,low cost and almost no invasion. Therefore, the distributed fiber sensing technology drawsmore and more attention in recent years.This dissertation aims at the research on the key technologies of a portable optical fibervibration sensing system. The basic principles of interferometric distributed fiber opticsensor are analyzed, several kinds of interference structure are compared, and the unbalancedMach-Zehnder interferometric optical structure, which has the advantages of being simple,stable, and easy for demodulation, is selected. To realize this system, the hardware platformand the software system are also designed, including all the parts necessary, like the driver ofthe laser, the conditioning part of detector signal, the temperature regulator of the lasermodule, and the management part of the power. The driver of the laser performs well inproviding stable and controllable current for the laser, ignoring step input, power surge andelectrostatic discharge. The conditioning circuit of detector signal has the characteristics ofstrong noise suppression and low voltage drift, and gives the signal outside of the band anattenuation of more than-40dB. The temperature regulation circuit is also of high stability,low steady-state drift and good dynamic characteristic, and makes the temperature controlerror only±0.2℃。The testing and analysis indicates that the system can accurately detect the vibrationalong the fiber and display the characteristics of the signal in time domain and frequencydomain with the maximum detection length up to70km. The system performs well instability, replicability and scalability, which makes it potential in applying in fiber identify ofcable laying, security monitoring of the buildings, earthquake monitoring and many otheroccasions where distributed vibration sensing is needed.