Abstract:

For the differential structure based optical fiber strain sensor, temperature and stress affect two gratings, and there is temperature and strain cross interference. The traditional temperature compensation algorithm does not consider the influence of the thermal expansion of the package structure on the center wavelength of the grating. There are some shortcomings in the theory of the algorithm, which are likely to cause measurement errors in the practical application of the project. In this paper, the sensitivity of the whole structure after encapsulation was analyzed, and the temperature sensitivity coefficient of the gratings was obtained by the experiment. The theoretical deduction was simplified and the strain measurement was carried out. The results show that after temperature compensation, the center wavelength difference between the two gratings is linearly related to the pressure. The linear correlation coefficient is 0.7 pm/Pa with a fit of 0.999 5, which can effectively suppress the effect of temperature on the wavelength.

Key words: temperature compensation, fiber Bragg grating, strain measurement, differential structure