Method and apparatus for optical sensing

  • US 11,079,269 B2
  • Filed: 07/11/2019
  • Issued: 08/03/2021
  • Est. Priority Date: 05/27/2009
  • Status: Active Grant
First Claim
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1. An apparatus for monitoring seepage along a dam or a dyke, the apparatus comprising:

  • an optical fiber distributed acoustic sensing system, the optical fiber distributed acoustic sensing system comprising an optical sensing fiber deployed in use along the dam or dyke and arranged to receive an input optical signal and propagate the received optical signal along its length; and

    an acoustic source located in use within a body of fluid contained by the dam or dyke, or within the dam or dyke itself;

    wherein the optical fiber distributed acoustic sensing system is arranged in use to process light backscattered and/or reflected from along the optical sensing fiber as the optical signal travels therealong, the light being backscattered and/or reflected in dependence on acoustic signals incident along the length of the optical sensing fiber, the backscattered and/or reflected light being processed to determine a relative optical phase modulation along at least one section of the optical sensing fiber to thereby measure a strength of an acoustic signal generated by the acoustic source, and to determine areas of seepage in the dam or dyke based thereon;

    wherein the optical fiber distributed acoustic sensing system is arranged in use to detect a louder acoustic signal in areas of seepage, wherein areas of seepage provide low acoustic impedance paths for acoustic wave transmission.

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