Multi-span sensing using wavelength / frequency multiplexing, synchronized receiver, and coherent signal processing

Abstract

A multi-span distributed acoustic sensing (DAS) system may include: a DAS transmitter, operative to transmit an optical sensing signal over an outbound path, where the optical sensing signal comprises a plurality of wavelengths. The multi-span DAS system may further include an optical cable, arranged over a plurality of spans to conduct the sensing optical signal along the outbound path, a given span of the plurality of spans extending for a distance of 10 kilometers or more, and a plurality of loopbacks, distributed over the plurality of spans, and arranged to conduct a Rayleigh backscattered signal to a return path, where the Rayleigh backscattered signal is derived from the optical signal. The multi-span DAS system may further include a receiver, to receive and to process the Rayleigh backscattered signal, wherein a time delay is applied to an electrical signal derived from the Rayleigh backscattered signal according to a wavelength of the Rayleigh backscattered signal.

Dependencies are inferred from the claim text.