Study On Sensing Signal Demodulation Technique For Distributed Fiber Bragg Grating With Interference

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 distribute measure is multiplexing, which includes Wavelength division multiplexing (WDM), Time division multiplexing (TDM), spatial division multiplexing (SDM) and the combination of any of them.The multiplexing about FBG not only reduces the cost of sensors, but also minishes the volume of the whole system. The demodulation method contributes in how the sensors work, 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.Firstly, 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.Secondly, this thesis focuses on the basic 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. Then it 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 faced now.Thirdly, on the basis of above analysis, a distributed FBG sensor demodulation system based on nom-balanced M-Z interferometer demodula- tion technique was designed. The system can simultaneously realize the demodulation of three channels after the designing of optic-route, electro-circuit, the data acquisition using of DAQ2005 and programming with Lab VIEW software using spectrum analysis.Lastly, a signal simulation phase meter based on Lab VIEW is designed. It uses the signal module instead of the Data Acquisition Module, and design random noise,A / D converter quantization error and so on. It makes the signal dealt with have the same Characteristics such as Acquisition of experimental data signals, and makes the simulation experiment have more research value.