Researchon Design Of Distributed Raman-basedoptical Fiber Temperature Sensing System And APD In Geiger Mode

With the development of science and technology, more and moretemperature measurement technologies have appeared. Distributed optical fibertemperature measurement technology has characteristics of instantaneity,continuity and anti-electromagnetic interference. It has developed rapidly withdevelopment of optical fiber communication technology since1977, and hasbeen widely applied into the production of daily life now. This technology isdivided into distributed Raman temperature sensing technology and distributedBrillouin temperature sensing technology. The latter began to develop later inthe late1980s, and now has been used by companies in Japan, Canada andSwitzerland to make practical production, while few similar products areproduced in our country. Compared with the Brillouin temperature measurementtechnology, distributed Raman temperature measurement technology developedearlier and rapidly due to its simple technology, and has been applied intoproducts at home and abroad.At present, distributed Raman temperature measurement system has beenwidely applied to power plants, tunnels, bridges, buildings, constructionbuildings, etc. Real-time temperature monitoring in these places has become particularly important, therefore the demand for DTS system is also increasing,which will prompt distributed Raman temperature measurement system to befurther optimized.Research on distributed Raman temperature measurement system can beclassifies into two types: optimize the sensor and optimize experimental device.The former is to extend the sensing distance effectively by improving method ofdata processing and changing structure of experiment (such as method of laserpulse coding, etc). The latter is optimized by improvement of laser (stability ofpulse laser), choose of WDM and control of APD.Researches on distributed Raman measurement system have been conductedas following:(1) Production of Raman scattering spectra and principle of temperaturemeasurement are learned carefully, and impacts on Raman temperaturemeasurement system caused by various demodulation way are compared.(2) The most stable laser is decided by analysis of the pulse laser, which ishelpful for reduction of impact on the follow-up data processing caused bychange of pulse width.(3) Researches on APD, analyzer noise factors and relationships betweenAPD gain and ambient temperature, bias, incident power are conducted.(4)Feasibility of APD in the Geiger mode is analyzed and the APDtemperature bias system is designed to guarantee the work of APD in Geigermode. (5)APD bias control system is analyzed and double temperature controlsystem is designed to guarantee temperature change on both ends of APD isbetween0℃-0.02℃.