Optical fiber distributed acoustic sensing for the leakage diagnosis using modal separation algorithms

With the expansion of urban scale and the passage of time, water supply pipeline networks leakage has become increasingly severe. Although acoustic detection methods have been widely applied due to their non-destructive characteristics, existing data-driven models exhibit poor generalization capability and weak noise resistance in complex leakage scenarios. To address these limitations, this study incorporates the physical propagation characteristics of leakage acoustic signals in pipelines, proposing a modal separation filtering methodology applicable to water supply pipeline networks through the integration of optical fiber distributed acoustic sensing system with modal separation algorithms. Specifically, a large-aperture sensing array was constructed along pipelines using optical fiber distributed acoustic sensing technology. Signal modal identification was achieved through analysis of wavenumber-frequency domain characteristics in sensing signals, followed by the establishment of frequency-wavenumber domain filters to realize modal separation. Numerical simulations were conducted to evaluate the impact of various factors on the stability of this methodology. Experimental results confirm the reliability of the proposed approach. The modal separation technique reduced localization errors from 61% to 4%. This methodology effectively resolves the challenges of modal aliasing in leakage acoustic signals and wave velocity uncertainty, demonstrating significant noise resistance advantages while enhancing the safety and resilience of water supply pipeline networks.