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 (PGC) demodulationalgorithm. 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/√Hz and a signal to noise ratio about 30.45dB is achieved. The maximum sensing length and the spatial resolution of the Φ-OTDR system are 10km and 6m with pulse repetition rate at 10kHz and 6m fiber delay in MI with interrogating pulse width of 30ns.
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