Study On Imaging Spectrograph Method For FBG Sensing Interrogation Techniques

This work is financially supported by the National 863 High Technology Project, and National Science Foundation projects. Fiber gratings are one type of developing fast passive fiber devices in recent years. As sensing element, they encode the sensing information in a wavelength form, which are their distinguished advantages over other transducers. That not only make the sensing information does not depend on loss of the system or fluctuation of the source power but also decrease the cost of sensing system and realize multipoint and distributed sensing. So the fiber grating sensing array interrogation has been a hotspot. Although fiber grating sensors utilize the wavelength to sense the parameters such as strain, temperature, pressure and etc., the fiber grating sensing will be difficult when multi-parameters are applied to them and the fiber grating sensors increase in number. Therefore, lots of researchers are interested in fiber grating sensing interrogation techniques. With the development of the fiber grating sensing network, the number of fiber grating sensors increase quickly, so the real-time sensor data collecting and disposing are necessary, that is data fusion. In the fiber grating sensing network, lots of data are not only disposed in time, but also analyzed and summarized, finally the judgment and recognition are generated. So the research of data fusion of fiber grating sensing network is a hotspot.In this dissertation, we mainly focus on the research and realization of fiber Bragg grating (FBG) interrogation, including the principles and experiments of sensing and interrogation techniques. The details are described as follows:1. Generally introduce the sensing techniques, especially the present situation and development of fiber grating sensing technique and FBG sensing interrogation techniques. Especially introduce the theory and characters of the FBG sensing interrogation techniques, and analyze the advantage and disadvantage of the fiber grating sensing interrogation.2. Introduce the two parts of the FBG interrogation system in detail: phase grating and image sensor. First, describe the characters and the demultiplexing theory of the volume phase grating. Secondly, describe the theory and structure of the CCD, InGaAs image sensors, and compare some characters of them.3. Generally introduce the theory and the manufacturing method of the tilted grating, analyze the coupling of the tilted grating with the volume current method. and analyze the transmitting spectrum. We not only write the tilted grating and analyze its transmitting spectrum, but also make the research of the strain sensing and temperature sensing of the tilted grating. Then analyze the demultiplexing theory of the tilted grating and make a study on interrogation technique for FBG sensing based on the tilted grating.4. A novel fiber grating sensing interrogation system based on the titled grating and InGaAs image sensor is presented.5. With the combination of WDM/SDM techniques, the interrogation system for the fiber grating sensing based on the InGaAs image sensor and volume phase grating may realize the measurement of the multi-points and multi-parameters. The interrogation system not only has small size, high interrogation speed, but also has high repeatability and high reliability. So it shows a good prospect.6. The multi-sensor data fusion technique for fiber grating sensing array based on BP network is presented, and the data information collected from the fiber grating sensor array is proposed with the technique. Furthermore, we make the data fusion for the strain and temperature grating sensors at the same time, and the fusion results show that the data fusion based on BP network has not only high speed, but also high accuracy.