Patent ID: 7952720
Filing Date: 2011-05-31
Classification: G01B,G01D,G01M

Abstract:
1. An apparatus for locating the position of an event, comprising: a light source; a waveguide for receiving light from the light source so that the light is caused to propagate in both directions along the waveguide to thereby provide counter-propagating optical signals in the waveguide, the waveguide being capable of having the counter-propagating optical signals or some characteristic of the signals modified or affected by an external parameter caused by or indicative of the event to provide modified counter-propagating optical signals which continue to propagate along the waveguide; wherein the waveguide comprises a first arm for receiving the counter-propagating signals, and a second arm for receiving the counter-propagating signals, the first and second arms forming a Mach Zehnder interferometer; a detector for detecting the modified counter-propagating optical signals affected by the parameter and for determining the time difference between the receipt of the modified counter-propagating optical signals in order to determine the location of the event; polarisation controllers for setting the polarisation states of the counter-propagating optical signals; a main controller for controlling the polarisation controllers so that the output signals are phase matched; the main controller comprising, the processor being for setting the polarisation controllers to at least one pair of optimum polarisation states that achieve phase matched output signals.