Time-domain shifting-assisted cepstrum method for complex vibration signal positioning in forward-transmission distributed vibration sensing

Aging urban underground pipelines face growing risks, making early damage detection essential. Conventional monitoring methods have limited coverage and scalability. Forward-transmission distributed vibration sensing (FTDVS) can provide real-time condition assessment, but existing positioning methods cannot operate when multiple vibration events overlap in frequency, severely limiting practical application. To address the lack of this critical capability, we propose a time-domain shifting-assisted cepstrum method that extracts primary delays, suppresses dominant components through time-domain shifting, and analyzes residual signals to recover secondary delays. The proof-of-concept experiments results from a 34 km long sensing fiber under three scenarios demonstrate reliable multi-point positioning, achieving positioning accuracies as small as 12.7 m. The results are highly relevant to applications such as real-time pipeline surveillance, security monitoring, and smart city infrastructure assessment.