Long-range distributed localization method of tapping-based vibrations

To enable effective mapping of underground vibrations, particularly non-periodic impact signals propagating along pipelines, this paper proposes a non-periodic vibration localization method that integrates a Mach-Zehnder interferometer (MZI) with forward transmission distributed vibration sensing (FTDVS) technology. Non-periodic vibration signals are demodulated through optical phase modulation in the sensing fiber. Comparative experiments were conducted to evaluate the localization accuracy of the three algorithms: cross-correlation, time shifted standard deviation (TSDEV), and phase spectrum time-delay methods. Results show that both the cross-correlation and TSDEV algorithms provide higher localization accuracy for non-periodic signals, whereas the phase spectrum time-delay method exhibits reduced accuracy due to insufficient consistency in dominant frequency components. Experimental validation over a 60.32 km sensing fiber demonstrates that a localization accuracy of approximately 10 m can be achieved for non-periodic impact vibrations. Therefore, the proposed localization approach exhibits strong potential for long-distance vibration monitoring and fault detection in complex underground environments, particularly in pipeline systems.