Research And Implementation Of Distributed Fiber Optic Grating Sensors Demodulation System Based On Embedded Technology

Since its invention, FBG sensor has completed theoretic research and experiment demonstration, and becoming more widely used in many fields, such as structure health monitor, intelligent material, electric power industry, medical and chemical industry and so on. How to detect and measure the tiny excursion of the wavelength reflect from the FBG sensors, is the most crucial engineering researches for FBG sensors practical applications. Optical fiber spectrum analyzer with high resolving power can differentiate the tiny excursion, but this kind of upscale bench-scale equipment is expensive, the volume is huge, the examination speed is slow, the operation is complex, not suitable for the project application on the scene, and cannot obtain the parameter or output form directly which the applications needs.The FBG sensors demodulating technology has become the main barrier to limit its applications, also become the most important research direction in the optical fiber sensor technology and the key problem to be solved. Although a large number of research units in domestic and abroad have been done 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 a long way to go to the practical industrial mass productions.With the earlier period work and technical support of Wuhan University of Technology's optical fiber sensor technology research center, and the application background of the bridge health monitor, this paper researched the key technology of embedded FBG sensors demodulation system, which has the characteristic of distributional,multichannel,multi-point and high speed.Mainly includes following several aspects:1. Introduced the principle of FBG sensor, analyzed the sensing characteristic by temperature, stress and pressure and the cross sensitivity problems of FBGs;Analyzed some methods of distributed FBG demodulation system and the tunable F-P filter demodulating method is introduced in detail;Introduced several overseas representative FBG demodulating products, which provide the actualreferences for the paper's research work.2. According to the bridge health monitoring system framework based on the Internet technology, the scheme of "embedded system + PC computer" was adopted in this paper, double processing core structure of ARM7 and SoC MCU are used in the embedded system, and the paper analyzed and designed the hardware and software architecture from the overall.3. Adopted the UC/OS+LwIP embedded platform, transplanted it on to the experiment board designed in the laboratory, and designed the driver of network adapter, SIO, UART etc.4. Designed the essential function module in the system, the demodulation algorithm, as well as the communication protocol between some modules, implemented the distributed FBG sensor demodulation system based on the embedded technology.5. Designed and developed a monitoring service software run on PC, which has the function of long-distance monitoring, data storage, real-time monitoring etc.6. Performed a system test. The system can work at 250Hz and survey 180 FBG sensors at one time. The precision of the survey is lpm. It achieved the anticipated design goal approximately.