Multi-source aliasing suppression for distributed fiber acoustic sensing with directionally coherent enhancement technology

Abstract

Distributed fiber acoustic sensing (DAS) can detect almost all disturbances along the sensing fiber and is widely applied. However, the signals from multiple adjacent disturbance sources are superimposed, according to the sensing principle. A directionally coherent enhancement technology is demonstrated for DAS to suppress multi-source aliasing in air. In preliminary works, two situations are considered for feasibility verification. The submerged weak target signal is effectively extracted from strong broadband noise, and two different same-frequency signals from two sources are separately rebuilt with the same detected signal. As far as we know, this is the first time that the directionally coherent enhancement is proposed for DAS and the multi-source aliasing is suppressed. This technique will help DAS find new important foreground in acoustic detection of large-scale plants with many similar noisy devices, including discharge detection in high voltage substations and acoustic emission flaw detection in mechanical factories.

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“…4(b). Note that, this result is a simple stack of channel coverages over all 40-km fibers, and further array response can be obtained with conventional array beamforming technology [16], such as, larger array response coverage with well-designed beamforming parameters [17] (Yellowknife array [18], etc. ), directional observations for specific sources (nuclear tests [19], etc.…”

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“…x and the initial point of the channel,  is the angle of arrival of the acoustic signal [15]. When the far field acoustic signal reaches the sensing channel, the change of optical fiber refractive index is given by ( ) ( )…”