Method and device for measuring temperature and strain of isotactic ultralow-reflectivity optical fiber gratings simultaneously based on Brillouin scattering

Abstract

The invention discloses a method and device for measuring the temperature and strain of isotactic ultralow-reflectivity optical fiber gratings simultaneously based on Brillouin scattering. The method includes the steps that the ultralow-reflectivity optical fiber gratings are continuously and dynamically etched through monopulse laser energy based on the drawing tower technology to obtain high-capacity optical fiber grating array sensing fibers, wherein m optical fibers and 2*m optical switches are connected to serve as a sensing probe; the reflection center wavelength lambda[i] and Brillouin frequency shift v[i] of each optical fiber grating are obtained through a high-speed CCD wavelength demodulation module and a Brillouin frequency shift heterodyne demodulation module; solving is carried out according to the Brillouin frequency shift and temperature and strain parameters of the optical fiber gratings to obtain the temperature and strain of the optical fiber gratings at each position. The method and device overcome the defects that the Brillouin sensing technology is low in precision and low in speed, simplify high-capacity ultralow-reflectivity optical fiber grating array optical fiber cabling complexity, improve high-capacity ultralow-reflectivity optical fiber grating array optical fiber cabling operability, overcome the cross sensitivity of the temperature and strain of the optical fiber gratings and improve distributed sensing detection precision.

Description

technical field [0001] The invention relates to a quasi-distributed identical weak fiber grating sensing and its demodulation technology, in particular to a method and device for simultaneously measuring the temperature and strain of an identical weak fiber grating based on Brillouin scattering. Background technique [0002] Temperature and strain are two key test parameters for structural health checks of large systems. The stress state of the local key positions of the structure is directly related to the safe service state of the structure, and the temperature has a greater impact on large-volume structures such as concrete dams and foundation pits. The action of temperature and stress often leads to damage such as microcracks inside the structure. Simultaneously and accurately measuring the temperature and strain of large structures has always been an engineering challenge due to the cross-sensitivity of temperature and strain. [0003] The quasi-distributed fiber grati...

AI Technical Summary

Problems solved by technology

[0004] The technical problem to be solved by the present invention is to provide a method and device for simultaneously measuring the temperature and strain of an identical weak fiber grating based on Brillouin scattering, which can overcome the small capacity of the sensing unit in the quasi-distributed sensing of the existing fiber grating. The insertion loss introduced by the position of the fiber grating and the fiber fusion point is large, its mechanical resistance cannot meet the engineering requirements, and the distributed Brillouin optical fiber sensor has slow response and low measurement accuracy. The present invention has large capacity, no welding The intensity of point and fiber grating is the same as that of optical fiber, and the temperature and strain of the sensing area can be detected at the same time, and the detection accuracy, detection speed and reliability are high.

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