Distributed Fiber-Optic Sensor Using Forward Travelling Light In Polarization Maintaining Fiber

A new method of distributed fiber sensing is presented which uses a polarization maintaining fiber as the sensing fiber and a frequency modulated laser diode as the light source. The mode conversion caused in the fiber by a perturbation to be measured generates an optical beat signal in the forward travelling light. The magnitude and location of mode conversion can be real time detected from the amplitude and frequency of the beat signal, respectively.