Low cost security perimeter based on a Michelson interferometer

We have designed a fiber optic sensor for perimeter security based on a Michelson interferometer. Both arms of the interferometer are embedded in a single specially designed cable that is laid under the protected perimeter. Each arm in a cable has a different protective buffer. The transfer of the disturbance caused by the intruder significantly differs between both arms of the interferometer, causing a large phase shift for even the smallest of disturbances. This eliminates the need for complex opto-electronic demodulation schemes traditionally employed in interferometric signal interpretations. Instead, interferometric signal is directly detected and analyzed in frequency domain.