A fiber grating geoacoustic sensing probe and sensing system

Abstract

The invention provides a fiber grating geoacoustic sensing probe, which includes an optical fiber, a weak chirped grating, a spring, a mass block, a weak chirped grating, and a cylinder body. One end of the spring is connected to the mass block, and the other end is connected to the cylinder body. Connection; one end of the optical fiber is glued to the quality block, and the other end is glued to the barrel. The two chirped gratings have the same reflectance spectrum, low reflectivity gratings with reflectivity lower than 1%, and are arranged outside the strain sensing working area to avoid the grating itself being affected by stress. The invention also discloses a sensing system based on the geoacoustic sensing probe, which can realize large-scale multiplexing of multiple probes. The invented sensing probe has a simple structure and high sensitivity. The time-division multiplexing sensing system based on the probe can flexibly configure the number and sensitivity of sensors according to specific application scenarios, and realize large-scale and wide-area sensing monitoring. Good application prospects.

Description

technical field [0001] The invention relates to the technical field of sensors, in particular to an optical fiber grating acoustic sensing probe and a sensing system. Background technique [0002] Debris flow ground sound means that during the flow of debris flow, the mixed particles will collide with the mountains along the way, generating vibration with a specific frequency. This vibration propagates along the rocks on the ditch bank to generate debris flow ground sound. By monitoring the ground sound of debris flow, early warning can be given to the occurrence of debris flow, so as to maximize the time for disaster prevention and mitigation, and effectively reduce the degree of disaster loss. However, compared with the monitoring of seismic waves, the ground sound intensity generated by debris flow is low, and it decays quickly during the propagation process on the shallow surface. The maximum propagation distance is about 100 meters, and the significant frequency is arou...

AI Technical Summary

Problems solved by technology

The existing "point-type" fiber grating sensor fixes the fiber grating on a mechanical structure (such as a cantilever beam), and realizes vibration sensing through mechanical structure transmission. Its sensitivity can basically meet the requirements of debris flow ground acoustic monitoring, but it is difficult to conduct Large-scale multiplexing is not easy to deploy in a wide area; distributed optical fiber sensing technology (such as optical fiber Brillouin sensor (BOTDA), optical fiber Raman sensor (DTS)) can better meet the requirements of large-scale monitoring, However, the detected sensing signal is weak, and the signal needs to be extracted through large-capacity data processing, and the real-time performance is not good.

[0003] In order to improve the sensitivity and multiplexing capability of fiber optic vibration sensors and realize the large-scale and high reliability monitoring of debris flow ground sound, some researchers have introduced the sensing scheme of fiber optic hydrophones (see "Liu Yuliang, He Jun et al. Optical fiber seismic wave detection Progress in Laser and Optoelectronics. 2009,11:21~28."), using DFB fiber laser technology to convert vibration changes into wavelength changes, and then demodulate and amplify through non-equilibrium Michelson interferometer This wavelength change realizes high-sensitivity geoacoustic sensing, but this solution needs to write a high-reflectivity grating on the active optical fiber, the preparation process is complicated, the number of reusable sensors is limited, and the system construction cost is high, so few in the field Related reports on civil applications

Other optical fiber sensing technologies, such as fiber grating Fabry-Perot (FFP) interferometer, etc., are difficult to amplify the sensing signal in the optical domain, the sensitivity improvement is very limited, and the system is complex and not practical

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