Study On Interferometric Distributed Optical-fiber Perimeter And Perturbation Location Technology

Interferometric distributed optical fiber sensing technology is a new technologydeveloped in1990s and in that it has high sensitivity and suits for long distance sensing,this technology gains more and more attention and research by people. A novelinterferometric distributed optical fiber sensing system based on Fox-Smith structure isproposed in this paper, which is simplicity and has high sensitivity and positioninglocation accuracy. It turns to be a feasibile method for long distance distributed opticalfiber sensing.This paper studied on current distributed fiber sensing technology, mainly focus oninterferometric distributed optical fiber sensing technology based on Sagnacinterferometer structure and Mach-Zehnder interferometer structure. Considering theirshortcomings, a distributed sensing system based on Fox-Smith structure sensing systemis designed. Thoretical analysis and simulation is made on system structure and phasereduction algorithm. Influence of the core component3×3coupler and Faraday rotationmirror been analyized on this sensing system. Polarization stability is discussed throughJones Matrix and using Matlab stimulate the consequence, which shows that usingFaraday rotation mirror can improve the stability of this system.Hence improves system’sreliability.An experiment on this distributed sensing system shows: along34.793km assensing fiber and achieves an average deviation of±83m, which testified that thissystem is feasible for long distributed optical fiber sensing and the phase reductionalgorithm is validity.For the demand of this distributed sensing system, receiving and sending module aredesigned.As for the receiving module, analyze of design in detail and circuit noise aremade on photoelectric conversion circuit and preamplified circuit. As for the sendingmolule, detailed design and analysis are made on constant current source design andtemperature control circuit. An experiment on the relationship of input and output ofreceiveing module shows that conversion slope will be smaller when the light input is very weak. Measurement of the different of light source stability as temperature change,the result shows that parameters of light differs when temperature lower than-15oC, andlight stability is normal when the temperature between-15oC and50oC.Research on distributed fiber sensing system in this paper provided a novel structurewhich has important significance and practical value on long distance moniting andpositioning.