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Detection of strain in fiber optics cables induced by narrow-band signals

  • US 9,976,920 B2
  • Filed: 09/14/2015
  • Issued: 05/22/2018
  • Est. Priority Date: 09/14/2015
  • Status: Active Grant
First Claim
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1. A method, comprising:

  • transmitting a narrowband signal into a formation using a transmitter located in a wellbore, wherein the narrowband signal is modified by passage through the formation and the formation reflects at least a portion of the narrowband signal back to the wellbore resulting in a modified narrowband signal;

    sensing the modified narrowband signal with an optical waveguide positioned in the wellbore;

    transmitting a source signal along a length of the optical waveguide, the source signal being modulated due to an interaction between the modified narrowband signal and the optical waveguide and thereby resulting in a backscattered return signal;

    sampling the backscattered return signal at less than a Nyquist rate and obtaining an undersampled backscattered return signal; and

    processing the undersampled backscattered return signal to obtain an amplitude of the modified narrowband signal sensed with the optical waveguide.

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