Fiber Grating Distributed Sensing System And Its Application In The Coal Mine Safety Monitoring

As one of the most rapidly developed passive fiber devices in recent years, Fiber Bragg grating (FBG) can reflect special wavelength which changes with temperature or strain. FBG sensor is a new type of sensor, and it has excellent temperature and strain response properties, which is a novel fiber photonic device with rapid development in these years and has broad and good applications in the fiber sensing field. The key technology to realize distributed measure is multiplexing, which includesWavelength division multiplexing(WDM), Time division multiplexing(TDM), Spatial division multiplexing (SDM) and the combination of any of them.The multiplexing about FBG make many of FBGs share in one source and one demodulation system which not only reduces the cost of sensors ,but also minishs the volume of the whole system. The demodulation method contributes in how the sensors work, the range of the sensors' application and their performance, so Wavelength demodulation is one of the most important techniques to achieve a distributed FBG system.The purpose of this paper is to discuss the demodulation system design and application research of strain and temperature sensing network of the distributed FBG.Chapter 1: On the basis of the deep researches of domestic and overseas literatures, the mechanism of the optical fiber grating sensors and the categories of FBG were generally introduced. The development trend of FBG sensing and several questions need to be solved in the practical application were summarized.Chapter 2: This thesis focuses on the obasic theoretical and technical researches on the optical fiber grating sensors, including coupled model theory of FBG, and the sensitivity coefficient of strain/ temperature sensor are the most important parts in this article. We designed the stress and the temperature test based on the theory of FBG Experimental data and the curve fitting is calculated by means of the computer. The simulated results are in excellent agreement with the practical results.Chapter 3: This article introduces the demodulation principle of distributed FBG sensors and some methods of FBG multiplexing, sums up the demodulation solutions of distributed FBG sensors and the problems facing now.Chapter 4: On the basis of above analysis, a distributed FBG sensor demodulation...