| The project is from the scientific research fund Doctor items(20030056017)of the ministry of education. The aim of the research paper is to discuss and set up a basic study on the Fiber Grating Sensors.Fiber grating, because of its great advantages and widely application scopes in the fields of the civil and military projects, has been concerned by the global reasearchers in recent years as one of the sensor components. Fiber gratings are very suitable for forming the the fiber array and can be applied in structure real-time monitoring, which makes multiplexing technology of the fiber grating be a research hotspot currently.The paper has done some theoretical research of basic characteristic, sensing theories and demodulation technology on Fiber Bragg Grating(FBG) sensors. According to the theories, the paper advanced and accomplished a set of FBG multiplexing sensing system which is based on non-balanced M-Z interferometry and Space Division Multiplexing(SDM). By the experiment of strain sensing property, the feasibility of the system is approved.The work of the project includes as follows:1. According to the theory of coupling, the law of light propagation in fiber grating has been studied, the even cycle transmission response characteristic of FBG was deduced, and the relationship among the refractive index modulation depthδn eff, grating length L and fiber grating characteristic has been analysed as well. The strain and temperature sensing models of FBG were also made. Aiming at cross-sensitive phenomenon, the paper studied several solutions about how to eliminate it.2. By discussing the demodulation methods and multiplexing technology of fiber grating, the paper built a new FBG multiplexing sensing system. The system, based on SDM, loaded deflection by tuning with an isosceles triangle cantilever. Modulation and Demodulation were made by non-balanced Mach-Zehnder interferometer and signal processing system the paper designed. Finally phase data were displayed. |
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