The Design And Implementation High-speed Fiber Grating Demodulation System Based On SOPC

Since the FBG birth to maturity has been applied to engineering,Accurate detection of the reflected wavelength drift,Wavelength encoded signal demodulation is one of the key technologies of FBG sensor.To study the FBG sensor demodulation technique, four issues must be addressed:First, FBG sensor based on grating wavelength as a medium, percepted the changes in the external physical parameters through the wavelength shift.To widen the scope of measurement must use broadband light source.In order to improve the resolution, emission linewidth(This will certainly greatly reduce the power efficiency of wide light sources) will be narrowed.This requires how to improve the demodulation system sensitivity in case of using low-power light source; Second, how to achieve high dynamic range, high accuracy, rapid scanning frequency;Third, the cross sensitivity can not be ignored, that is how to distinguish the correct wavelength shift is caused by stress or temperature;Fourth,to improve the detection sensitivity, high-performance monochromator or spectrometer must be used.However, these instruments are expensive and difficult to carry, while such equipment is not designed for temperature measurement and strain, is not conducive to on-site testing. Soluting these problems effectively for develope low-cost, high-speed, high-resolution, large dynamic range, multi-channel multi-grating multiplexing, easy to carry and easy to operate the FBG sensor demodulation system has great significance.This topic will study FBG Reflection spectrum signal demodulation method's limitations and diversity base on FBG sensor technology,through sampling optical power of the center frequency of Reflection spectrum of the system front,choose a variety of signal processing systems,using DSP digital signal processor to fit spectral curve which can improve the sensitivity and accuracy,using artificial neural network algorithm to optimize cross-sensitive error.FPGA is as the core of high speed data transfer, via USB Serial communication with PC for data exchange to realize the display of dynamic real-time measurement and basic operations,to realize high-speed dual-FBG sensor multiplexing demodulator, which is based on DSP Builder of FPGA and dual soft-core of SOPC Builder's.First, designing based the F-P filter's tunable demodulation principle, detecting the wavelength of the FBG reflection spectrumusing the I-MON spectral power meter. To improve the measurement accuracy and sensitivity through curve fitting program to obtain the wavelength peaks.Second,analyzed temperature-stress the formation mechanism of cross-sensitivity in the fiber bragg grating sensor measurements and the impact on the measurement results,to obtain cross-sensitivity optimization program which is based on artificial neural network algorithm,through the weighted study error of the feedback system.Make the sensitive value separate from the observed value as far as possible. Raising system's resolution.Third,In view of the above front-end for signal acquisition and measurement wavelength nature,using embedded soft-core DSP to process the floating point of signal to improve processing speed.Combining with the high overall performance of SOPC Builder to design high-speed FBG sensor demodulation system based on FPGA platform.