DISTRIBUTED FIBER-OPTICAL ACOUSTIC SENSING DEVICE AND METHOD BASED ON DIGITAL DUAL-CHIRPED PULSE MODULATION

摘要

A distributed fiber-optical acoustic sensing device based on digital dual-chirped pulse modulation is used for long-distance distributed acoustic wave detection. The device adopts a dual-polarization four-parallel Mach-Zehnder electro-optic modulator (3) to perform chirped pulse modulation respectively in an X-polarization direction and a Y-polarization direction. A chirped pulse light signal in the X-polarization direction is used as a detection light pulse, is amplified by an erbium-doped fiber-optical amplifier (9) and is then introduced into a fiber optic sensor (12). A chirped pulse light signal within a continuous sweep range of the Y-polarization direction is used as reference light, and is mixed with, by an optical coupler (13), a backscattering chirped pulse light signal carrying optical phase and frequency information of all of the positions of the fiber optic sensor (12). An interference optical signal is separated, by two fiber optic polarization beam splitters (14, 15), into two polarization directions to be detected and received. Phase, amplitude, and frequency of a position subjected to acoustic waves of the fiber optic sensor (12) are acquired by data processing. A distributed fiber-optical acoustic sensing method based on digital dual-chirped pulse modulation is also provided. The invention combines fiber optic sensing and transmission and solves the difficulty of reconciling demand for both long distance and high resolution in distributed fiber optic acoustic signal sensing.