Study On The Computer Information Process System Of The Distributed FBG Sensors

Fiber Bragg Grating is a fiber optic device that is expected to be of great applicative prospect in fiber communication. Nowadays the manufacturing and application research on FBG is turned into hot field in the world' s fiber optics technology. As a sensor, FBG can be immune from light source disturbance and system loss by transforming sensing information into its reflecting wavelength shift. Besides, FBG is of good reliance, immune from electromagnetic signals and corruption, and can be constructed as FBGs network by being put together on a single fiber so as to realize distributed sensing, which is an unexampled merit for FBG. The key point in FBG sensors lies in precise measurement of minute shift of Bragg reflecting wavelength, that is demodulating the coded signals of wavelength. Though it is can be achieved by Optical Spectrum Analyzer (OSA) with high resolution, OSA can not be applied into practical situation because of its huge-size and high-cost. So developing high-resolution and low-cost FBG demodulator is the key issue when it comes to FBG sensors industrializations. Although a large number of researchers in domestic research units have been doing a lot of research and investigations on the demodulation methods of FBG, most of the researches are still in the phase of lab experiments and have not yet met the requirements of the practical industrial mass productions.In this paper, a high-resolution, cheap, easy-to-operate, distributed FBG wavelength demodulation system is presented. This system can meet the requirements of the practical industrial applications and display the real-time changes of measurands. In this system, a tunable fiber Fabry-Perot(F-P) filter is used to detect the changes of the wavelengths of the FBGs, then both the tunable control signal and thesignal indicating the changes of the wavelength transmitted by an A/D electric transmission circuit are input into computer. The corresponding changes of the measurands can be obtained by filtering, analysising and processing the experimental data by using the computer information process system.Firstly, this paper deals with the theoretical feasibility of the demodulation scheme and its performance and then clarifies the scheme in details. Secondly, experiments are performed to testify the resolution of the system and analysis of the results is made. Finally, approach to improve the performance of the system is put forwards based on the analysis of the experimental results.The following work has been done in this paper:(1)Analyze the principle of fiber Bragg Grating, and investigate the temperature and strain sensing characteristic of FBG.(2)After analyzing the existed FBG demodulation method, according to problems confronted in practical fiber optical sensing application, Construct FBGs network to do multi-sensing demodulation experiment to detect the distributed temperature variables. Design and settle a set of optical and electrical device system, and programming parallel port muti-channel data collection and data processing software.(3)Process and analyze the experimental data, figure out the temperature characteristic curves and fix the exact value of each sensing FBGs in the network. Based on the results of experiments, summarize the advantages and disadvantages of the demodulation scheme, and propose the improving method.