The Pulse Light Source Oriented POTDR System Application

In recent years, with the rapid development of the optical fiber sensing technology andthe increase of people’s living standard, the application of fiber sensor is becoming more andmore widely in daily life, especially in the field of perimeter security and distributedmeasurement. As one of them, the fiber sensing technology based on polarization which hasgreat advantages in resolution, sensitivity, SNR and measurable parameters, will have verybroad application prospects and great market potential.The principle of optical fiber sensing system based on polarization (POTDR,Polarization Optical Time Domain Reflectometer) is analyzing backscattering pulse sensingsignal of the optical fiber link, using time information to position the polarization changepoint and monitoring the sensing information quickly and effectively. In POTDR system, thebig size and hight price of the commercial pulse light source result in hight-cost andunwieldy, which is not conducive to produczation of POTDR. Moreover, the pulse lightsource of POTDR is different in some parament with ordinary optical source which need todo some special design.Firstly, the thesis discusses POTDR’s system principle detailedly.Secondly, the characteristic parameters of pulse light source are analyzed, the light sourceparameters design requirements are presented and the pulse semiconductor light sourcedriver circuit is designed. Finally, using self-made pulse light source, the POTDR sensingsystem is set up, acquiring rapid detection and location of the disturbance successfully.The main work of this thesis covers the following aspects:(1) A large number of relevant researches on the distributed fiber sensors iscarefully studied. The basic principle of POTDR system is studied. And, the luminescenceprinciple and characteristic of the semiconductor laser diode parameters is analyzed.(2) The direct modulation principle, design method of laser drive circuit andannounceets are discussed detailedly. According to the theory research requirement, thepulse light source drive circuit is designed, including: the pulse signal generating circuit,modulation current generating circuit and peripheral protection circuit. In addition, therelated characteristics of pulsed laser source are tested.(3) Using self-made pulse light source, the distributed optical fiber sensing system is perfectly structured. By exerting disturbance on optical fiber link artificially, the systemcollects back scattering sensing signal. Then through the signal data processing and analysisof algorithm, the fast detection and localization of disturbance is realized.