DETECTION OF STRAIN IN FIBER OPTICS CABLES INDUCED BY NARROW-BAND SIGNALS

摘要

A method may include transmitting a narrowband signal into a formation using a transmitter located in a wellbore. The narrowband signal is modified by passage of 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 having a first frequency. The method also includes sensing the modified narrowband signal with an optical waveguide positioned in the wellbore, transmitting a source signal along a length of the optical waveguide, and obtaining a backscattered return signal from the optical waveguide. The backscattered return signal is sampled at a second frequency that is less than the Nyquist rate of the modified narrowband signal. The method further includes processing the backscattered return signal to obtain an amplitude of the modified narrowband signal.