Research on Peak-detection Algorithm for High-precision Demodulation System of Fiber Bragg Grating

Abstract

In order to improve the detection accuracy of wavelength, the filtering and curve fitting technologies were applied in the FBG wavelength demodulation system based on tunable F-P filter. These methods could realize the accurate peak-location of output signals of the photo detector. According to the characteristics of noise, the FIR low-pass filter was designed to filter the obtained light power signals so as to provide the input signals with high SNR for the peak-detection algorithms. By analyzing and comparing several typical peak-searching algorithms, the algorithm of Gauss formula nonlinear curve fitting (L-M) was chosen to fit the digitized light power signals. The experimental results show that L-M fitting algorithm reduces the mean square error by 7.5% compared with the Gauss fitting algorithm. For the Gauss signal in the wavelength demodulation system designed in the paper, the L-M algorithm has lower mean square error than other peak-searching algorithms. This algorithm is suitable for FBG wavelength demodulation system based on tunable F-P filter. It can efficiently raise the accuracy of wavelength demodulation system.

A precision fiber Bragg grating interrogation system using long-wavelength vertical-cavity surface-emitting laser

“…But it will lead to large errors when the noise is high. Some curve fitting techniques (e.g., Gauss curve fitting, Gauss formula nonlinear curve fitting, and artificial neural network) can effectively improve the detection accuracy [12,13]. But they are generally complicated and are not suitable for micro-controller systems.…”

Efficient detection of multiple FBG wavelength peaks using matched filtering technique

“…In this context several research works have been carried out. For single peak detection, the statistical techniques like centroid detection [10], polynomial curve fitting, direct peak method [11], Gaussian non-linear method [12] etc. have been reported [13].…”

Improved FBG interrogator considering FFP filter nonlinearity and investigation into performance limit

“…The first issue is developing algorithms to determine the Bragg peak wavelength with adequate wavelength resolution and accuracy. Recently, various techniques for determining the Bragg peak wavelength, such as the maximum detection algorithm, the cross-correlation demodulation algorithm, and fast phase correlation (FPC), have been developed [12][13][14][15][16]. Pfrimer et al [12] proposed a method for tracking the temperatures controlled by a feedback loop in tracking the photodiode current of the convolution value of a tunable FBG.…”

“…Tosi [14] presented an algorithm based on the Karhumen-Loeve transform for accurate tracking of FBG sensors, which exhibited accuracy superior to that of correlation-based algorithms. Wang et al [15] introduced a peak-detection algorithm using the finite impulse response (FIR) low-pass filter and Gauss' formula nonlinear curve fitting, which can efficiently increase the accuracy of the wavelength demodulation system. Allan et al [16] demonstrated an FBG strain sensor interrogation system based on the correlation implemented on an embedded digital signal processor.…”