A phase-sensitive optical time-domain reflectometry system with an electrical I/Q demodulator

We propose an electrical I/Q demodulation scheme to decrease the sampling rate and computational cost in coherent phase-sensitive Optical Time-Domain Reflectometry systems. The IF signal from the photon detector and the local-oscillator from the acoustic-optic modulator driver are splited into two parts, respectively. One of local-oscillators is 90°shifted, then the signals and LOs are cross-mixed and the outputs are low-pass filtered to obtain the I/Q signal. Besides of the save of computational cost, the sampling rate and data storage is reduced at least 1.6 times. At last, a quantitative measurement of a 50 Hz vibration is successfully demonstrated in the experiment.