A Novel SNR Enhancement Method for Complex Multimode Signals in ϕ-OTDR Systems Using SVMD and Shifting Window Pearson Correlation Coefficient

To improve the quality of seismic data acquired by distributed acoustic sensing (DAS) systems and mitigate phase noise in phase-sensitive optical time domain reflectometry (Φ-OTDR) systems, a denoising method based on successive variational mode decomposition (SVMD) and the shifting window Pearson correlation coefficient (SWPCC), termed SVMD-SWPCC, is proposed. The phases obtained by the Φ-OTDR systems are adaptively decomposed into several intrinsic mode functions (IMFs) using SVMD. The proposed SWPCC method is used to accurately identify highly correlated components from each IMF, enhancing the overall signal-to-noise ratio (SNR). The SVMD-SWPCC algorithm improves upon existing approaches that determine which modes need to be retained on the basis of global correlation coefficients. By introducing a shifting window, the impact of unrelated components within IMFs on the Pearson correlation coefficient (PCC) is mitigated, thereby significantly improving the accuracy of the correlation assessment. The experimental results for single-frequency, multi-frequency, sweep-frequency, and wide-frequency impact signals show that the SVMD-SWPCC algorithm effectively mitigates the phase noise in Φ-OTDR. Compared to existing methods, SVMD-SWPCC offers advantages such as an improved SNR and robust adaptability. It has also been successfully applied to denoising in controlled electromagnetic seismic experiments and sledgehammer impact signal tests.