Design Of Fiber Bragg Grating Sensing Demodulation System Based On

Fiber grating sensor is a kind of sensor which is gradually mature. It has many excellent characteristics which other kinds of sensors do not have. In recent years, the sensor technology based on fiber grating has developed with high speed, because of its electrical insulation, anti-electromagnetic interference, acid corrosion, small size, light weight, high sensitivity and so on, it ha s been widely used in coal, petroleum, chemical, aerospace, building structural health monitoring, dynamic monitoring of complex mechanical systems and other fields.There are some products based on different solutions related o n the fiber grating sensor demodulation at home and abroad now. These products always perform not so well because of the low demodulation frequency, or the complex structure, or the expensive price, which greatly hindered the popularity of the fiber grating sensing technology. The hardware system based on FPGA can take full advantage of the high-speed, high-customizable, low-cost and simple structure, and then achieve the high-speed fiber grating demodulation solution with lower cost. From the fiber grating sensing system components and sensor demodulation principle, we focus on the design of fiber grating sensor demodulation peak searching algorithm and hardware demodulation modules. The main work is as follows:1. Depth study of the composition and working pr inciple of grating sensor demodulation system, comparative analysis of the existing domestic and international classic demodulation scheme.2. For fiber grating sensor demodulation key technology, which is the peak detection technology, we had improved the existing paper-based smoothing and least square method peak searching algorithm, the improved peak searching algorithm can not only accurately calibrated optical fiber peak grating reflection spectrum, it can also calculate the fiber grating center wavelengt h of the reflected signal spectrum position, peak bandwidth, and area. The accuracy of the algorithm is 10-4.3. We use Verilog to design each module of fiber grating sensing demodulation system digital processing circuit, such as the data acquisition and A / D module,that the conversion rate of A/D is 100 KHz, the resolution is 8 bit, theSRAM module,the value display module.4. We use DSP Builder library to design digital filter model in MATLAB, MATLAB and Modelsim and Q uartus II software complement each other, the filter model designed in MATLAB has done RTL simulation in Modelsim. At last, we transfer the filter module into hardware description language, which can be compiled in Quartus II.5. Finally, we do a system test to verify the function of the digital demodulation system which is made up by A/D module、SRAM module、FIR module and display module. From the acquisition port, we get acquisition analog voltage signal,the signal go through SRAM module and FIR module,then it comes to the display module and shows to us the specific value. From the system test, we get the analog voltage acquisition range of the digital demodulation system,it is from 3.6 V to 4.0 V. It has a certain practical value.