Distributed optical fiber Brillouin sensing device and method thereof for detecting temperature and strain synchronously

Abstract

The invention relates to a distributed optical fiber Brillouin sensing device for detecting temperature and strain synchronously and a method for detecting the temperature and the strain synchronously by use of the device. The method is based on the linear relation among the frequency shift change of the spontaneous Brillouin scattering in the optical fiber, external temperature change and external strain change, a compound sensing optical fiber is formed by two different types of sensing optical fibers, and the variation of the temperature and the strain can be distinguished at the same time through different responses of the two optical fibers to the external temperature change and the external stress change. According to the device and the method, the temperature change and the strain change in a sensing area can be detected at the same time, and the detection precision of an optical fiber distributed sensor based on spontaneous Brillouin scattering can be improved.

Description

technical field [0001] The invention relates to an optical fiber sensor, in particular to a distributed optical fiber Brillouin sensing device and method for simultaneously detecting temperature and strain. Background technique [0002] Distributed optical fiber sensors have broad application prospects in industry, national defense and other fields due to their strong anti-electromagnetic interference ability, good electrical insulation, and distributed sensing. The optical fiber distributed sensor based on spontaneous Publisher Scattering (hereinafter referred to as BOTDR) has a long sensing distance and single-end incidence. The distributed optical fiber sensor will be widely used in large structures such as pipelines, offshore oil platforms, oil wells, dams, embankments, bridges, buildings, tunnels, cables and the like. [0003] The amplitude and beat frequency of the Brillouin backscattered light spectrum in the sensing fiber are linearly related to the external tempera...

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Problems solved by technology

However, in this scheme, the demodulation of the signal is more complicated: the spontaneous Raman scattered light needs to be filtered out from all the backscattered signals with a fiber grating filter, and the light intensity of the back Rayleigh scattered signal needs to be detected to obtain Obtain the temperature signal corresponding to Raman scattering; while the self-published Liouin scattering is demodulated by coherent detection method to obtain the beat frequency change of the spectrum of the Brilliant light signal, and the external stress can be known by using the temperature signal obtained from the previous demodulation Variety

The difficulty and complexity of signal demodulation limit the practical application of this scheme

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