The main factors limiting the measurement distance of DAS system and improvement methods

With the increasing application of distributed acoustic sensing (DAS) in long-distance scenarios such as oil/gas pipeline monitoring and perimeter security, critical challenges persist in mitigating signal attenuation, noise accumulation, and distance-dependent degradation of sensing accuracy, while existing approaches struggle to simultaneously achieve ultra-long- range detection with high sensitivity and optimal optical signal-to-noise ratio (OSNR). The article analyzes several factors limiting the sensing distance in DAS systems, including system sensitivity, dynamic range, and optical signal-to-noise ratio (OSNR). A 150 km fiber-optic sensing experimental setup was constructed, employing distributed fiber Raman amplifiers to suppress the dynamic range of echo signals. By adopting coherent signal split-beam sampling and weak-strong signal splicing techniques to enhance the system's dynamic range, combined with fiber Bragg grating filtering to achieve high SNR, the system realized a maximum effective sensing distance of 125 km.