Denoising method based on VMD-PCC in φ-OTDR system

Abstract

To improve the signal-to-noise ratio (SNR) of vibration signal in phase-sensitive optical time domain reflectometry (φ-OTDR) system, a vibration signal denoising method based on variational mode decomposition (VMD) and Pearson correlation coefficient (PCC) is proposed. The phase signal demodulated by I/Q demodulation is further processed by a denoising method consisting of K layers VMD, where K was determined by calculating the ratio of adjacent intrinsic mode functions (IMFs) center frequencies, the Pearson correlation coefficient (PCC) estimation between each component and phase signal, and distortion and noise casting by discarding the IMF components with the PCC less than a threshold of 0.4 and the residual component of decomposition. The denoising method was verified in a 2 km φ-OTDR system in the scenarios of single 200 Hz frequency vibration at one position, two single frequencies of 200 Hz and 500 Hz vibration at two positions with minimum separation distance defined by the pulse width, and a multi-frequency vibration of 200 Hz, 1200 Hz and 2500 Hz at one position. And the demodulated phase signal by I/Q demodulation was processed by the proposed method, and further compared with the wavelet decomposition, empirical mode decomposition (EMD), ensemble empirical mode decomposition (EEMD) and complementary ensemble empirical mode decomposition (CEEMD). Experimental results show that the VMD-PCC method is superior to the other methods compared in improving the SNR of vibration signals and has excellent adaptability and effectiveness in φ-OTDR system.