Research On Ultra-weak Fiber Grating Sensor Demodulation System

With the progress of society and the development of science and technology,sensor technology has been widely used.Ultra-weak FBG,as a new type of fiber Bragg grating sensing field,has become one of the irreplaceable research directions in the sensing field due to its advantages of small loss,high mechanical strength and strong multiplexing ability in the optical signal transmission.One of the research directions,the new generation of fiber grating sensor network composed of ultra-weak fiber grating has the characteristics of large capacity,long distance,high precision and so on,which can meet the needs of thousands of monitoring points in large projects.Based on the research of fiber grating sensor technology at home and abroad,this paper takes the demodulation technology and system of large capacity fiber grating sensor network as the research object,studies the spectral characteristics of ultraweak fiber grating array,in view of denoising and peak detection,an effective denoising scheme and corresponding demodulation algorithm improvement are proposed to realize the large capacity and high precision demodulation of the sensor network.The signal processing part is an important link to ensure the accuracy of the demodulation system.In this paper,the collected signal of the sensor demodulation system is studied,and it is improved and reconstructed on the basis of the wavelet threshold to remove the noise.Experiments show that this method not only overcomes the discontinuity of the hard threshold function itself,but also avoids the inherent deviation of the soft threshold function,improves the accuracy of signal reconstruction,and achieves a good anti-manic effect on the preprocessing of the sensor signal.The accurate positioning of the center wavelength of the spectrum is the key to measuring the demodulation technology of the sensor network.This paper analyzes the commonly used peak-finding algorithms and their advantages and disadvantages.Anti-noise high-speed peak-finding algorithm for capacity sensing network.The algorithm introduces weighting factors into the least squares(WLS)fitting algorithm combined with asymmetric Gaussian correction(AG)to locate the center wavelength of the reflection spectrum,and proposes that the WLS-AG algorithm can achieve high-precision peak finding.Finally,the performance of several different peak-finding algorithms is compared by testing to verify the feasibility of the algorithm proposed in this paper.The test platform of demodulation system for large capacity ultra-weak FBG sensor network is built.The temperature sensing experiment shows that the system built by the algorithm proposed in this paper can achieve a linear fit of more than 0.997 in the temperature test range of 0?~50?,and the average temperature error of the demodulation system is about 0.3?,which has a good reference value.