Distributed acoustic sensing measurements of active and passive sources up to 1 kHz

Distributed Acoustic Sensing (DAS) is a technology that utilizes telecommunication fiber-optic cables as dense acoustic sensors by transmitting pulses of light along the cable and measuring backscatter from inhomogeneities in the fiber. The technology provides a means of dense samples (as low as several meter channel spacing) over long ranges (upwards of 100 km). An experiment was conducted in Puget Sound, near Seattle WA, in which a DAS cable and co-located hydrophones collected passive acoustic data for ∼9 days, in addition to data broadcast from an active, impulsive source at 1, 5, and 10 m depth from multiple locations on the first and last days. The DAS data sampled the field at 2 kHz, with 6.38 m channel spacing over ∼3.5 km of underwater cable, most of which at ∼100 m depth. We explore the capabilities of the DAS measurements at frequencies up to 1 kHz from different types of sources, considering the advantages and limitations of measurements on the cable relative to the hydrophones.