Patent ID: 9201161
Filing Date: 2015-12-01
Classification: G01B,G01V

Abstract:
1. An optical detection system for monitoring a pipeline, the optical detection system comprising: (a) a host node in the vicinity of, or remote from, a pipeline to be monitored, the host node including (a) an optical source for generating optical signals, and (b) an optical receiver; and (b) a plurality of fiber optic sensors local to the pipeline to be monitored, the plurality of fiber optic sensors for converting at least one of vibrational and acoustical energy to optical intensity information, each of the fiber optic sensors including: (1) at least one length of optical fiber configured to sense at least one of vibrational and acoustical energy; (2) a reflector at an end of the at least one length of optical fiber; and (3) at least one field node for receiving optical signals from the host node, the field node transmitting optical signals along the at least one length of optical fiber, the field node receiving optical signals back from the at least one length of optical fiber, and the field node transmitting optical signals to the optical receiver of the host node, wherein each of the fiber optic sensors includes a linearized Sagnac interferometer, wherein the linearized Sagnac interferometer includes a 3×3 fiber optic coupler, a delay coil of optical fiber, a depolarizer, and a 2×2 fiber optic coupler, wherein an output of the optical source is connected to a first input lead of the 3×3 fiber optic coupler, and wherein a second input lead of the 3×3 fiber optic coupler is connected to the optical receiver of the host node, and wherein a third input lead of the 3×3 fiber optic coupler is configured such that it does not support guiding light, and as such, reflected light can not travel along the third input lead back to the 3×3 fiber optic coupler, and wherein a lead of the delay coil is connected to an output lead of the 3×3 fiber optic coupler, and another lead of the delay coil is connected to an input lead of the 2×2 fiber optic coupler.