The Research On Fiber Grating Sensing Demodulation System Based On FPGA

The fiber Bragg grating sensing technology is applied to the temperature monitoring of the power equipment has great advantage, but now the fiber Bragg grating demodulation equipment at home and abroad are mainly based on the structural safety monitoring of large applications, there are some disadvantages for a small application, such as large volume and high cost etc, so this article use the high speed digital processing of FPGA and highly integrated characteristics of SOPC, and designed a fiber Bragg grating(FBG) sensing demodulation system with FPGA as the control core.This paper first described several demodulation methods of FBG sensing system, then determined to adopt the F-P filtering demodulation scheme with FPGA as control core through the analysis and comparison of these methods to realize the FBG sensing signal demodulation, and detailed described the system design scheme. The system choose the low cost chip EP2C70F896 of Cyclone? as the main control chip in the design, and generated sawtooth signal to realize the control of F-P filter by controlling the high speed DAC904;Realized high speed data acquisition of sensor signal by controlling the high speed ADS805;Stored buffer data through the FPGA inner FIFO and process it; Finally realized data transmission with the host computer through RS232 serial port communication technology.The hardware circuit of the system mainly includes drive circuit of filter, photoelectric detection circuit, high speed A/D data acquisition circuit, FPGA peripheral circuit, PC communication interface circuit. Software mainly includes sawtooth wave produces module,12 bits parallel A/D sampling control module, storage module, PC communication module.Finally simulated the hardware circuit and the software of the system in the quartus software.The results show that using FPGA digital design method to generate the sawtooth wave signal is meet requirement of the filter; and realized the sensor signals high-speed data acquisition.This paper adopted the control method based on FPGA and the SOPC system on chip solution to complete the demodulation system design, it shorten the development period of design, and reduced the cost of application system.