Undersea pipeline intrusion detection system using low-frequency guided acoustic waves and distributed optical fiber

摘要

A method and an apparatus for intrusion detection. The apparatus includes an acoustic source, a laser light source, a pressure-sensitive optical fiber including a first end and a second end. The second end is connected to the laser light source and oriented toward the acoustic source. The laser light source generates a laser pulse traveling through the pressure-sensitive optical fiber toward the acoustic source. The laser pulse includes a time-of-flight. The acoustic source generates an acoustic wave. The acoustic wave includes a plurality of evanescent wave fronts. The plurality of evanescent wave fronts, upon scattering from a non-uniform material region, radially contracts the pressure-sensitive optical fiber to alter the time-of-flight of the laser pulse along the pressure-sensitive optical fiber by increasing the fiber length.