Grating multifunctional sensor applied in extreme low temperature environment

Abstract

The invention discloses a grating multifunctional sensor applied in the extreme low temperature environment. The grating multifunctional sensor comprises multiple Bragg fiber gratings having different initial wavelengths, light signals of the multiple Bragg fiber gratings are gathered through a fiber splitter to an output fiber, and the multiple Bragg fiber gratings are arranged in a two-dimensional or three-dimensional space and are used for measuring and monitoring planar and cambered surface multi-direction strain and temperature, spatial three-dimensional multi-direction strain and temperature and structure / material internal multi-direction strain and temperature. The grating multifunctional sensor is advantaged in that problems of poor mechanical performance, complex multi-direction and multi-physical variable measurement and incapability of realizing spatial three-dimensional strain and temperature measurement existing in a Bragg fiber grating sensor in the prior art are solved, and planar and cambered surface, spatial three-dimensional and structure / material internal multi-direction strain and temperature synchronization measurement and monitoring are realized.

Description

technical field [0001] The invention relates to the technical field of sensors, in particular to a grating flower multifunctional sensor used in an extremely low temperature environment. Background technique [0002] Fiber Bragg grating sensor is a kind of fiber optic sensor. Its sensing process is to obtain sensing information through the modulation of the fiber Bragg grating wavelength by external physical quantities, and can realize direct measurement of physical quantities such as temperature and strain. [0003] In the prior art, fiber Bragg grating sensors mainly measure or monitor a single direction and a single physical quantity for the structure or material to be measured. Most of them use a temperature range above 77K, and mainly measure the physical quantity of the structure or material surface. To sum up, under the extremely low temperature environment (77K ~ 4.2K), in the process of realizing the present invention, the inventor found that there are at least the ...

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Problems solved by technology

[0004] (1) The measurement and monitoring of the three-dimensional direction of space and the strain and temperature inside the structure / material cannot be realized: in an extremely low temperature environment (77K~4.2K), the current fiber Bragg grating sensor is only for a single direction on the surface of the structure / material, The measurement of a single physical quantity cannot realize the measurement and monitoring of the three-dimensional direction of space and the strain and temperature inside the structure / material;

[0005] (2) The mechanical properties of fiber Bragg gratings in extremely low temperature environments (77K~4.2K) are not good: at present, the strain and temperature sensors based on fiber Bragg grating sensing technology are mostly used in the temperature range above 77K, but in In an extremely low temperature environment (77K~4.2K), since the fiber Bragg grating itself is a brittle material, and a coating material (or packaging material) with poor mechanical properties is used in an extremely low temperature environment (77K~4.2K), it will cause The demodulated signal of Fiber Bragg Grating has "multi-peak phenomenon", which may even damage the Fiber Bragg Grating

[0007] One is to use multiple single-point fiber Bragg grating sensors (only one Bragg grating sensor on one fiber) to cooperate / combined use, and install them on the surface of the measured object at different angles to measure strain or temperature. This method greatly increases the number of output optical fibers (used to transmit optical signals to the optical fiber demodulator), which brings great inconvenience to the experimental operation;

[0008] Another way is to use a quasi-distributed fiber grating sensor. The sensor of this structure is to arrange multiple Bragg grating sensors on an optical fiber at intervals along the optical fiber. "When measuring, it is necessary to "bend and move" all its fiber Bragg gratings to the "fixed point" position, but this method will not only lead to intricate fiber routing, but it is very likely that in an extremely low temperature environment (77K ~ 4.2K ), because the "bending radius" of the optical fiber is too small to damage the optical fiber, which brings great inconvenience to the experimental operation;

[0009] In addition, in the low temperature environment, the current fiber Bragg grating sensor needs to perform temperature compensation when performing strain measurement or monitoring, which brings great inconvenience to the experimental operation.

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