Phase-Sensitive Optical Time Domain Reflectometer Based on Phase-Generated Carrier Algorithm

We propose a novel approach to generate distributed fiber sensing system based on phase-sensitive optical time domain reflectometer (Φ-OTDR) and phase-generated carrier demodulation algorithm. An unbalanced Michelson interferometer is introduced at the receiving end of the system. The back Rayleigh scattering light from a certain position along the sensing fiber would interfere to generate interference light signal versus time, whose phase carries the sensing information. Phase-generated carrier demodulation algorithm is proposed and carried out to recover the phase information. A single frequency vibration event is applied to a certain position along the sensing fiber and we realize to demodulate it correctly. The noise level of the phase sensitive OTDR system is about 3 × 10^-3 rad/VHz and a signal to noise ratio about 30.45 dB is achieved. The maximum sensing length and the spatial resolution of the Φ-OTDR system are 10 km and 6 m with pulse repetition rate at 10 kHz and 6 m fiber delay in MI with interrogating pulse width of 30 ns.