High signal-to-noise ratio acoustic sensor based on multimode optical fiber

Abstract

The invention discloses a high-signal-to-noise-ratio acoustic sensor based on a multimode optical fiber. The high-signal-to-noise-ratio acoustic sensor comprises a light source part, a modulation part, a mode multiplexing / demultiplexing part, a reference light part, a detection part, a data acquisition part and a sensing part. The light source part, the modulation part, the mode multiplexing / demultiplexing part and the sensing part are sequentially connected, the light source part splits reference light through a first optical fiber coupler of the reference light part, the detection part performs beat frequency on a signal output by the mode multiplexing / demultiplexing part and the reference light, and the output signal is connected to the data acquisition part. According to the invention, a sensing optical fiber is changed from a single-mode optical fiber to a multimode optical fiber, multiple modes in the multimode optical fiber are utilized to sense external sound wave / vibration information, then de-multiplexing is carried out at a detection end or a signal end, and signals detected by N modes are combined, superposed and averaged after diversity, so that the ground noise can be reduced, and the signal-to-noise ratio of the system can be improved; and the sensitivity and the strain resolution of the system are improved.

Description

technical field [0001] The invention relates to the field of acoustic sensors with high signal-to-noise ratio, in particular to an acoustic sensor with high signal-to-noise ratio based on multimode optical fibers. Background technique [0002] Distributed optical fiber acoustic sensing technology uses the phase change of Rayleigh scattered light caused by the acoustic signal acting on the sensing fiber to realize the distributed detection of the acoustic signal. In recent years, with the rapid development of distributed optical fiber sensing technology, optical fiber distributed acoustic detection has also become a hot research direction in the field of optical fiber sensing. As one of the most representative optical fiber distributed acoustic sensing technologies, phase-sensitive optical time domain reflectometer can realize distributed, long-distance and real-time quantitative detection of optical fiber link vibration and acoustic waves. At present, the optical fiber dist...

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Problems solved by technology

【Chen, D.A., et al.(2017). "Phase-detection distributed fiber-optic vibration sensor without fading-noise based on time-gated digitalOFDR." Optics Express 25(7):8315-8325.], but frequency diversity The number is limited by the system bandwidth, and it is difficult to achieve large-scale multiplexing

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