Optical fiber distributed monitoring system and method

An optical fiber distributed monitoring system, comprising a laser, an acousto-optic modulator, a phase matching interferometer, a photoelectric detector and a phase demodulation module,

• wherein the laser is configured to output continuous laser light which is transmitted to the acousto-optic modulator, and the acousto-optic modulator is configured to chop the continuous laser light into pulsed light;
• the pulsed light is transmitted into a sensing optical fiber, the sensing optical fiber is configured to output, upon detection of a vibration or acoustic wave signal, Rayleigh backscattering light containing the vibration or acoustic wave signal, and the Rayleigh backscattering light is transmitted into the phase matching interferometer;
• the phase matching interferometer is configured to split the Rayleigh backscattering light into a first portion of Rayleigh backscattering light and a second portion of Rayleigh backscattering light, for phase-modulating the first portion of Rayleigh backscattering light by applying a first modulation wave to a first arm of the phase matching interferometer, and for phase-modulating the second portion of Rayleigh backscattering light by applying a second modulation wave to a second arm of the phase matching interferometer, wherein the phase-modulated first portion of Rayleigh backscattering light and the phase-modulated second portion of Rayleigh backscattering light, with a phase difference therebetween in a range of 0-2π, interfere with each other to generate interference light;
• an amplitude difference between the first modulation wave and the second modulation wave is greater than or equal to an amplitude difference threshold enabling an optical phase difference between the two arms of the phase matching interferometer to be 2π, and each of the waveform of the first modulation wave and the waveform of the second modulation wave is any one of a triangle wave, a sawtooth wave and a sine wave;
• the phase matching interferometer is further configured to transmit the interference light into the photoelectric detector;
• the photoelectric detector is configured to convert the interference light into an interference electric signal and to send the interference electric signal to the phase demodulation module;
• and
• the phase demodulation module is configured to phase-demodulate the interference electric signal based on a Hilbert algorithm to obtain vibration or acoustic wave information.