Robust broadband distributed acoustic sensing based on adaptive reference selection

In this work, we propose a robust compensation scheme for broadband frequency-division-multiplexed (FDM) distributed acoustic sensing (DAS), in which a switchable frequency channel is used as the reference to compensate sensitivity and phase-offset mismatches among different frequency components. Unlike conventional FDM DAS compensation schemes that rely on a single common reference with a fixed frequency component and are consequently vulnerable to coherent fading at certain fiber locations, the proposed approach enables adaptive reference selection among frequency components by constructing pulse pairs with different frequency combinations. This allows the frequency channel with the highest signal-to-noise ratio to be selected as the reference for compensation at each fiber location. Experimental results show that, at a sensing distance of 50 km, a maximum spurious-suppression of 24.3 dB is achieved under quiescent conditions, while a spurious-free dynamic range (SFDR) of 24.0 dB is obtained for a 3.5 kHz vibration signal. Meanwhile, enhanced spurious-suppression is consistently maintained along the entire sensing fiber.