Apparatus and method for distributed acoustic sensing

An apparatus (100′) for distributed acoustic sensing, the apparatus (100′) comprising means for:

• performing (200) a plurality of distributed acoustic sensing, DAS, measurements (M-1, M-2, . . . ) by applying a plurality of optical interrogation signals (IS-1, IS-2, . . . ) to an optical waveguide (1) and receiving a respective plurality of backscattered response signals (RS-1, RS-2, . . . ) from the optical waveguide (1) in response to the plurality of interrogation signals (IS-1, IS-2, . . . ), the response signals (RS-1, RS-2, . . . ) having delay-resolved spectra comprising delay-resolved spectral features of the optical waveguide (1), wherein at least some of the delay-resolved spectral features are shifted in frequency, wherein at least two of the response signals comprise a same part of the delay-resolved spectral features, determining (202), based on the plurality of response signals (RS-1, RS-2, . . . ), an aggregated response (AR) of the optical waveguide (1).

A method for distributed acoustic sensing, the method comprising:

• performing (200) a plurality of distributed acoustic sensing, DAS, measurements (M-1, M-2, . . . ) by applying a plurality of optical interrogation signals (IS-1, IS-2, . . . ) to an optical waveguide (1) and receiving a respective plurality of backscattered response signals (RS-1, RS-2, . . . ) from the optical waveguide (1) in response to the plurality of interrogation signals (IS-1, IS-2, . . . ), the response signals (RS-1, RS-2, . . . ) having delay-resolved spectra comprising delay-resolved spectral features of the optical waveguide (1), wherein at least some of the delay-resolved spectral features are shifted in frequency, wherein at least two of the response signals comprise a same part of the delay-resolved spectral features, determining (202), based on the plurality of response signals (RS-1, RS-2, . . . ), an aggregated response (AR) of the optical waveguide (1).