A Distributed Simultaneous Measurement Method of Temperature and Strain

Abstract

A method for simultaneously measuring distributed temperature and strain, which uses a Brillouin optical time domain reflectometer and a coherent optical time domain reflectometer sharing the same set of optical system and circuit system as the sensing measurement system, and the sensing measurement system takes turns Work in BOTDR mode and COTDR mode, measure Brillouin scattering spectrum and Rayleigh scattering spectrum distributed along a single single-mode sensing fiber, and detect the frequency shift of Brillouin scattering spectrum and Rayleigh scattering spectrum , and then according to the characteristics that the frequency shift of the two scattering spectra is linearly related to temperature and strain, a binary linear equation system about temperature and strain is established, and the temperature and strain at each position of the sensing fiber are obtained by solving the equation system, and then obtained Temperature and strain distribution along the entire sensing fiber. The invention greatly reduces the complexity and manufacturing cost of the system, has no special requirements on the Brillouin frequency shift coefficient of the optical fiber, and expands the applicable range of the measurement system.

Description

technical field [0001] The invention relates to a method for realizing simultaneous measurement of distributed temperature and strain by using a single optical fiber, belonging to the technical field of measurement. Background technique [0002] Due to the advantages of strong anti-electromagnetic interference, easy installation of equipment, good insulation, and high sensitivity, optical fiber sensing technology has received more and more attention in the fields of electric power, construction, and civil engineering. BOTDR (Brillouin Optical Time Domain Reflectometry, Brillouin Optical Time Domain Reflectometry) measures the temperature and strain by measuring the frequency shift of the Brillouin scattering spectrum of the incident light pulse in the optical fiber, but there is a temperature and strain cross sensitivity of the Brillouin frequency shift The problem, resulting in indistinguishable temperature and strain, limits the application of this technique. COTDR (Coher...

AI Technical Summary

Problems solved by technology

BOTDR (Brillouin Optical Time Domain Reflectometry, Brillouin Optical Time Domain Reflectometry) measures the temperature and strain by measuring the frequency shift of the Brillouin scattering spectrum of the incident light pulse in the optical fiber, but there is a temperature and strain cross sensitivity of the Brillouin frequency shift problems, resulting in indistinguishable temperature and strain, limiting the application of this technique

COTDR (Coherent Optical Time Domain Reflectometry, Coherent Optical Time Domain Reflectometry) measures the temperature and strain by measuring the Rayleigh scattering spectrum frequency shift of the incident light pulse emitted by the coherent light source in the optical fiber, but there are also temperature and strain of the Rayleigh scattering spectrum frequency shift. Strain cross-sensitivity issues, resulting in indistinguishable temperature and strain, also limit the application of this technique

[0003] Distributed measurement of temperature can be carried out by using Raman scattering of optical fiber, but distributed measurement of strain cannot be carried out

[0004] At present, when using optical fiber sensing technology to measure distributed temperature and strain at the same time, the dual-fiber method is usually used. There are two schemes for this method. One scheme is that two optical fibers are laid in parallel, and the temperature of the Brillouin frequency shift of the two optical fibers , different strain coefficients, measure the Brillouin frequency shift of two optical fibers, and solve the temperature and strain through simultaneous equations. This method is only applicable to special customized optical fibers, and cannot be applied to communication optical cables or photoelectric composite cables.

Another dual-fiber solution is also to lay two optical fibers in parallel, one of which is only affected by temperature, and the other is affected by temperature and strain at the same time, and the Brillouin frequency shift of the two optical fibers is measured, through the simultaneous equations Solving for temperature and strain, this solution is also not suitable for already laid communication optical cables or photoelectric composite cables

In addition, the measurement method combining Raman optical fiber distributed temperature measurement technology with Brillouin technology can be applied to a single optical fiber, but this method requires two sets of optical path systems, the system structure is complex, the cost is high, and it is difficult to apply single mode fiber

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