KEYWORDS: Reconstruction algorithms, Signal to noise ratio, Denoising, Interference (communication), Sensors, Matrices, Signal processing, Chemical species, Fiber Bragg gratings, Detection theory
Aiming at the noise signal caused by external environment and sensor reuse in the demodulation system of large capacity fiber grating sensor network, a Threshold Retained Orthogonal Matching Pursuit (TROMP) reconstruction algorithm is proposed based on compressed sensing theory. In this algorithm, the useful signal can be effectively recovered from the noise signal by improving the threshold setting, atom selection and iteration stop condition. Experiments show that: TROMP algorithm can achieve ideal denoising and reconstruction effect under less observation value, the SNR of the system is increased by 10 dB, the root mean square error is less than 0.0071, and the number of cross-relations can reach 0.9999. Compared with similar algorithms, the running time is shortened by more than half, and the comprehensive performance of noise signal processing for FBG sensor system is better than other reconstruction algorithms.
Aiming at the poor accuracy of traditional single peak detection algorithm in fiber grating demodulation, this paper proposes a symmetry corrected Gaussian nonlinear fitting algorithm based on Hilbert transform (HT-EXG) for multi peak detection. The algorithm uses Hilbert transform to segment the input reflection spectrum and uses exponential modified Gaussian nonlinear fitting algorithm to correct and optimize its peak position, so as to achieve accurate positioning of the reflection spectrum. The experimental results show that the proposed HT-EXG algorithm improves the accuracy of FBG peak demodulation and the stability of the system. The average error of peak detection is less than 3 pm, and the system stability is better than 0.5 pm. It provides an accurate demodulation method for FBG sensor network peak detection.
The quality of the reflection spectrum of the Fiber Bragg Grating (FBG) will directly affect the performance of the grating sensor network. Aiming at the problem of quality detection of fiber Bragg grating sensor network prepared online, this paper proposes a reflection spectrum quality identification algorithm based on Support Vector Machine (SVM). Firstly, the characteristic information of the original reflection spectrum is extracted based on theory and simulation. Then the raw feature information is preprocessed using a "signal segmentation and search model" to find the approximate locations of the original reflection spectrum. Finally, the kernel function is used to optimize the SVM network model until the recognition accuracy of the reflection spectrum quality feature meets the requirements. 2000 groups of reflection spectrum characteristic data were put into SVM recognition network for training, the recognition effect reached 99.9%. Finally, the non-uniform temperature field is established, and the experimental results show that the algorithm can identify the distortion spectrum pattern of the fiber Bragg grating array with more than 99% accuracy. It effectively improves the recognition accuracy of reflection spectrum peak sag and distortion and provides a new idea for the quality detection of core components of fiber Bragg grating sensor network.
We propose an improved Gaussian curve fitting method based on the Hilbert transformation (HTG) to tackle the ineffectiveness of the traditional peak-seeking algorithm in detecting the multi-peak Fiber Bragg grating (FBG) reflection spectra. A five-point sliding filter is used to process the FBG reflection spectral signal, de-noise and smooth the noise, and select the optimal threshold point by the Hilbert transformation (HT). The sub-spectra of the multiple FBG reflection spectral signals were derived and the initial positioning of the spectral peaks were achieved. The Levenberg–Marquardt (LM) algorithm is used to extract the Bragg wavelength from the segmented sub-spectral signals as well as optimize the Gaussian curve fitting coefficients. The HTG-LM algorithm is then proposed, and is optimized and utilized to achieve precise positioning of the spectral peaks. The theoretical analysis and experimental results showed that the proposed HTG-LM algorithm could dynamically detect the multiple reflection spectra of the FBG sensing system with good stability, and at the same time, reduce the amount of peak-seeking data, which is highly beneficial to improve the signal demodulation rate. The peak detection accuracy of the proposed algorithm is better than 1 pm and the precision is better than 4 × 10 − 7 pm, which indicates that this HTG-LM algorithm provides an accurate demodulation algorithm for the FBG sensor networks. As a result, it is a promising multi-peak detection algorithm proposed by this paper to be applied to the FBG sensing systems.
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