Device and method for synchronous calibration of strain and temperature of distributed sensing optical fiber (cable)

Abstract

The invention discloses a strain and temperature synchronous calibration device and method of a distributed sensing optical fiber (cable), which comprises the following steps: when calibrating the strain coefficient, the optical fiber (cable) to be calibrated is first evenly wound on the outer wall of the calibration barrel, and gradually Add weights at each level, calculate the hoop strain of the calibration barrel under different loads according to the elastic modulus and Poisson's ratio of the calibration barrel, and use the optical fiber data demodulator to read the spectral information under various loads to establish the hoop strain and spectrum The relationship between the information, the gauge coefficient is calibrated; when the temperature coefficient is calibrated, the temperature control box is used to control the temperature of the calibration barrel, and the spectral information at different temperatures is obtained through the demodulator, and the temperature coefficient is calibrated. The invention can separately or synchronously calibrate the gauge coefficient and the temperature coefficient, can simultaneously determine the influence of the strain generated by the external force and the environmental temperature change on the spectral information, and analyze the cross effect between the two. The calibration results have the advantages of high precision and more conformity with actual application conditions.

Description

technical field [0001] The invention relates to the technical field of distributed sensing optical fiber (cable) sensor calibration, in particular to a strain and temperature synchronous calibration device and method for distributed sensing optical fiber (cable). Background technique [0002] In distributed fiber optic sensing systems, using optical fibers as sensors, changes in strain or temperature can be monitored in real time. When the external temperature or strain changes, the optical fiber wavelength, frequency and other spectral information changes are analyzed by the demodulator, and then the temperature or strain is obtained through theoretical calculation. Before using this method, you must first determine the gauge coefficient and temperature coefficient of the optical fiber under test in the theoretical formula. The two coefficients are related to the material of the optical fiber and are physical parameters of the optical fiber itself. They cannot be tested dir...

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Problems solved by technology

The equal-intensity beam method is to paste the optical fiber on the equal-intensity beam, and use the deformation of the equal-intensity beam to generate strain on the optical fiber. This method requires manual operation, the accuracy is very poor, and the calibration results have large errors, making it difficult to meet the requirements. Moreover, the length of equal-strength beams is generally less than 2 meters, and the spatial resolution of commonly used demodulators is generally greater than 1 meter. The data points obtained are too few and often not representative

In addition, the strain gauge or dial gauge is used to measure and calculate the strain of the equal-intensity beam, but there is glue between the equal-intensity beam and the optical fiber, which is not completely coupled, resulting in the strain of the equal-intensity beam being equal to that of the optical fiber. Strain cannot be transmitted directly, and corresponding errors will also occur

[0004] The fixed-point stretching method is to fix the optical fiber with a clamp on the displacement platform, accurately measure the distance between the two clamps, and use an electric or hydraulic displacement device to apply tension to the optical fiber. The displacement of the displacement platform is used as the deformation of the optical fiber in the stretched section. The functional relationship between the strain parameter and the actual displacement, after calculation, the strain coefficient of the optical fiber is obtained. The fixed-point stretching method is currently the most used method in the industry, but there are also shortcomings: The deformation causes the tensile deformation of the fiber core to be inconsistent with the actual displacement of the stage; Where the tension section joins, the measurement results change gradually rather than abruptly, and the Brillouin frequency shift within 1 / 2 spatial resolution distance at the end of the tension section is relatively small, which will make There is an error in the calibration of the optical fiber gauge factor

[0005] When calibrating the temperature coefficient of an optical fiber (cable), the constant temperature water bath / oil bath method is generally used at present, and it is mostly carried out in a high and low temperature box. Only the influence of temperature on the spectral information can be obtained, and the effect of strain and temperature changes on the spectral information cannot be obtained at the same time. Therefore, it is difficult to distinguish the cross-effect of strain and temperature on the monitoring readings in the actual application process, which limits further refined testing

In addition, traditional calibration devices cannot achieve simultaneous calibration of strain and temperature, and can only be calibrated separately, which has great limitations

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