Patent ID: 8395782
Filing Date: 2013-03-12
Classification: G08B

Abstract:
1. A method for locating physical disturbances occurring in a detection zone, comprising: coupling at least one signal source to two interferometers, each said interferometer defining two signal paths of substantially equal lengths, wherein said coupling comprises coupling a Mach-Zehnder interferometer with a Sagnac interferometer, wherein the input ends of the interferometers define one end of a structure and wherein the output end of the Mach-Zehnder interferometer and a center point of a Sagnac interferometer loop define an other end of the structure; arranging the signal paths such that at least parts of signal paths of said two interferometers overlap; causing the signals traveling along the parts of the signal paths that overlap to traverse the detection zone at least once; wherein a disturbance in the detection zone instills time variations in phase differences between the signals traveling along the signal paths of the two interferometers, at a point where the disturbance occurs; coupling at least one signal receiver to the output ends of the interferometers and configuring the signal receiver to measure said time variations in the phase differences between the signals traveling along the signal paths of said two interferometers; processing outputs of the signal receiver to derive two composite variables from the time variations in the phase differences, wherein a relationship between said composite variables varies with a location of the point of the disturbance, wherein the composite variables are derived in the form: where Φ wherein the composite variables have substantially identical waveshapes at a time lag of t determining the point in the detection zone at which the disturbance occurred, from the relationship between the composite variables, including said time lag.