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The Research Of Low-coherence Interferometer Based Distributed Optical Fiber Sensing System

Posted on:2012-01-22Degree:MasterType:Thesis
Country:ChinaCandidate:S Y ZhaoFull Text:PDF
GTID:2218330338970846Subject:Optics
Abstract/Summary:PDF Full Text Request
With the development of social production level, distributed optical fiber sensing system has been deeply studied and widely used in security inspection of intelligent materials, communication trunk, power transmission line, oil/natural gas pipelines and bridges. This system has many advantages, such as no sensing blind-zone, sensing network can be easily built, anti-electromagnetism interference and so on. Low-coherence interferometer based distributed optical fiber sensing system has become one of the key topics in this area for its simple configuration, lower cost and high reliability.However, because many problems still persist, such as signal processing time is long, the noises introduced by environmental vibration and temperature variance are difficult to be eliminated, this system's performance well be degraded in the practical application.In this paper, theoretical calculation and experimental analysis about low-coherence interferometer is given at first, then through adding two fiber Bragg gratings to improve the traditional hybrid configuration of Mach-Zehnder and Sagnac interferometer, a novel noise reduction configuration is proposed.The first chapter describes the development of optical fiber sensing system, its sensing theory, and thus developed distributed optical fiber sensing system; then quasi-distributed sensing technology and distributed sensing technology are briefly introduced, this part also summarizes the development of this technology at home and abroad; at last, the contents and innovations of this paper are mentioned.Chapter II mainly introduces the principle of low-coherence interferometer based distributed optical fiber sensing system and classify the different interferometer technique based sensing system, it also provides a theoretical basis for chapter III and chapter IV.Chapter III introduces the localization of the vibration signals based on low-coherence interferometer. In this chapter, we setup a hybrid configuration of Mach-Zehnder and Sagnac interferometer by using a 2X2 coupler. a:3×3 coupler, and a broadband light source, then we analysis the localization theory and verify the configuration's performance by experiments.In chapter IV, through improving the hybrid configuration of Mach-Zehnder and Sagnac interferometer and adding two fiber Bragg gratings, a novel noise reduction configuration is proposed in this paper. Theoretical analysis and simulation calculation show that this structure can well eliminate the noises accumulated during the long-distance sensing process, the value of residual noise has concern with the length of sensing fiber and the frequency of the noises, under typical conditions, it can be less than 1%.
Keywords/Search Tags:optical fiber sensing, distributed sensor, low-coherence interferometer, noise reduction, fiber Bragg grating (FBG)
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