Distributed Brillouin optical fiber sensing system based on coherent detection

Abstract

A distributed Brillouin optical fiber sensing system based on coherent detection comprises a pump laser and couplers. Lasers emitted by the pump laser are divided into two routes of detecting light through the first coupler. The first route of detecting light enters a Brillouin optical fiber annular laser device of a lower arm light path, and output Brillouin lasers serve as local oscillation light. The second route of detecting light enters a distributed Brillouin optical fiber sensor of an upper arm light path, and obtained backward Brillouin signal light with temperature and strain information serves as scattered light. After frequency mixing is conducted on the Brillouin signal light and the Brillouin lasers through the second coupler, the Brillouin signal light and the Brillouin lasers are connected to a photo-electric detector to undergo photo-electric conversion. The distributed Brillouin optical fiber sensing system based on coherent detection has the advantages that high nonlinearity optical fibers are adopted in the Brillouin optical fiber annular laser device, the output Brillouin lasers are small in line width and stable in frequency, and sensing precision is increased; the distributed Brillouin optical fiber sensor can measure temperature and strain signals at the same time, and therefore high-frequency detection is converted to low-frequency detection, cost is greatly saved, and system complexity is lowered.

Description

technical field [0001] The invention belongs to the field of optical fiber sensing, in particular to a distributed Brillouin optical fiber sensing system based on coherent detection. Background technique [0002] Distributed optical fiber sensor is a sensing method based on the principle of measuring scattered light generated when light waves propagate in optical fibers. Compared with traditional sensing methods, distributed optical fiber sensors have more advantages, mainly for the fact that the measured spatial distribution status and time-varying information can be obtained at the same time; environmental parameters distributed along the optical fiber can be monitored over the entire length of the optical fiber. Continuous measurement; in theory, the measured value can be regarded as a function of the length of the optical fiber position, so as to obtain any resolution; an optical fiber can be used to replace the traditional array of sensors consisting of hundreds of latt...

AI Technical Summary

Problems solved by technology

The traditional BOTDR uses the pump light as the local oscillator light, and the signal frequency after the beat frequency is about 11GHz, which puts forward high requirements on the bandwidth and sensitivity of the photodetector, which increases the difficulty of detection

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