SNR Enhancement Method for Φ-OTDR System Based on Sdr_SampEn-BiPSO-SVD Algorithm

To solve the problem of a low signal-to-noise ratio (SNR) of the vibration positioning curve in the phase-sensitive optical time-domain reflectometer (Phi-OTDR), a denoising algorithm based on spatial dependence recurrence sample entropy (Sdr_SampEn) and singular value decomposition (SVD) optimized by improved particle swarm optimization algorithm based on the Beer Antennae search (BiPSO) algorithm (Sdr_SampEn-BiPSO-SVD) is proposed. First, the Phi-OTDR system based on a heterodyne coherent detection structure is built, the vibration signal is obtained by the I/Q quadrature demodulation algorithm, and the noise source of the vibration signal is analyzed. Second, the mathematical principle and the denoising process of the Sdr_SampEn-BiPSO-SVD algorithm is established. Finally, the noise suppression capability of Sdr_SampEn-BiPSO-SVD algorithm is tested by simulation experiments and Phi-OTDR system experiments, and compared with wavelet, empirical mode decomposition combined with Pearson correlation coefficient (EMD-PCC), variational mode decomposition (VMD). The experimental results show that the SNR of vibration positioning curves at 1 Hz, 100 Hz, 500 Hz, and 1 kHz improved to 21.28, 29.08, 16.55, and 32.99 dB, respectively, and demonstrate the ability to identify multipoint vibration and improve the quality of multipoint vibration positioning signals. The feasibility and effectiveness of the algorithm have been proven in practical applications. This algorithm provides a new means for the application of the Phi-OTDR system in the field of seismic exploration.