Achieving fully distributed and fading-free acoustic sensing based on scattering-enhanced fiber.

Distributed acoustic sensing (DAS) based on scattering-enhanced fiber (SEF) eliminates interference fading, yet its reliance on discrete differentiation limits it to a quasi-distributed framework, leading to cross-unit signal distortion. We propose a fading-free, fully distributed SEF-DAS scheme that uses a frequency-domain phase-shift transformation. A targeted frequency-spectrum transformation reconstructs spatially complementary optical fields individually for each orthogonal polarization state. A rotational vector sum is then applied to aggregate and suppress interference and polarization fading, filling discrete sensing chasms. Experimentally, continuous, blind-spot-free acoustic field restoration with 5-m spatial resolution is achieved over a 26.4-km range, delivering a strain sensitivity of 2.21 nε/√Hz at the link terminal at 1 mHz.