Distributed fiber optic sensor with location capability

A spatially distributed sensor system, comprising:

• an optical conduit;
• an optical transmitter comprising a light source assembly for inputting depolarized light into the optical conduit, the optical transmitter being optically coupled to the optical conduit;
• a plurality of spatially distributed sensing elements spaced along and optically coupled to the optical conduit, each sensing element comprising a wave guide providing an optical path for to travel through sensing element and back into the optical conduit, wherein each sensing element of said plurality of sensing elements is structured to return light to the optical conduit with a first set of characteristics when the sensing element is in a first state and to return light to said optical conduit with a second set of characteristics when the sensing element is induced into a second state by a physical disturbance to it, and wherein the second set of characteristics are based on a change in the birefringence and/or interference patterns in the wave guide;
• and
• an optical receiver coupled to said optical conduit and configured to receive light from the sensing elements and output a signal indicative of the state of the sensing element.

A method of sensing a spatially localized effect, comprising:

• generating a pulse of polarized light and depolarizing said pulse of polarized light to form a pulse of signal light;
• transmitting said pulse of signal light along an optical conduit;
• splitting off a fraction of light from said pulse of signal light at each of a plurality of spatially distributed sensors spaced along an optical conduit and polarizing said fraction of light;
• and
• returning light to said optical conduit from each of said plurality of spatially localized sensors in an amount indicative of an effect being detected based on a change in the birefringence of one or more of the sensors,
• wherein at least one of said plurality of spatially distributed sensors is responsive to a mechanical effect to sense the presence of an intruder.