Analysis of Tunable F-P filter and Peak-Detection Algorithm in FBG Demodulation System

Abstract

The FBG demodulation system is introduced. The tunable ring cavity laser is used as the light source. The output wavelength of the tunable F-P filter is calibrated by the F-P etalon, and the F-P etalon is calibrated by the temperature compensation reference grating. By interpolation between two comb-shaped teeth of etalon, the center wavelength of the sensing grating between the two comb-shaped teeth is obtained, and the demodulation accuracy is improved. The Gaussian mathematical model of the spectrum is established, and the relationship between the fiber grating sensor with a bandwidth of 0.2nm and the tunable F-P filter with bandwidths of 0.01, 0.17 and 0.25nm is given. Through the comparison of Gaussian fitting, centroid method and orthogonal least square method, it is found that the measurement accuracy based on orthogonal polynomial least square method is second only to Gaussian fitting, but its operation speed and stability are greatly improved, and it is more suitable for FBG sensor network with large data volume.