Brillouin optical time domain analysis system and Brillouin optical time domain analysis method

Abstract

The invention relates to a Brillouin optical time domain analysis system and a Brillouin optical time domain analysis method. The system obtains dual-frequency optical carriers through modulating continuous light by an electro-optic modulation link, four different frequencies of detection light and dual-frequency pulse light are generated through a detection light generation link and a dual-frequency pulse light generation link, and the optical signal power for each frequency is below the nonlinear threshold; the dual-frequency pulse light is controlled to generate time delay through a first Bragg grating module to eliminate crosstalk of the dual-frequency pulse light, two ways of pump light are thus formed and are injected to an optical fiber, time delay compensation is carried out on Brillouin signal light formed due to interaction between the detection light and the pump light injected to the optical fiber through a second Bragg grating module, and finally, after signal processing, Brillouin frequency shift data of the optical fiber are acquired. Thus, nonlinear effects caused by single-frequency pulse light and over high signal optical power can be avoided, power demands of the pulse light are reduced, the signal-to-noise ratio of the system is improved, and non local effects caused by pump depletion can be reduced.

Description

technical field [0001] The invention relates to the technical field of monitoring, in particular to a Brillouin optical time domain analysis system and method. Background technique [0002] The distributed optical fiber temperature and strain monitoring system based on the principle of Brillouin scattering is widely used in power cables, tunnel tubes, etc. In the safety monitoring of major structures such as corridors, water conservancy projects, and long-distance oil and gas pipelines. However, at present, in the sensing fiber, the maximum incident light power of both pulsed light and continuous light is limited, the peak power of pulsed light cannot be higher than 100-150mw due to modulation uncertainty, and continuous light is finally limited by the amplified Self-Brillouin scattering, the power cannot be greater than 5mw, so the signal-to-noise ratio and distance cannot be improved by infinitely increasing the power of pulsed light and continuous light. The interaction...

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Problems solved by technology

[0005] Based on this, it is necessary to provide a Brillouin optical time domain analysis method for the low signal-to-noise ratio caused by pump depletion and nonlinear effects in the current long-distance Brillouin distributed optical fiber sensing system. System and method

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