Cubic fitting method of wavelength shift of optical fiber grating temperature sensor and a temperature measuring device

Abstract

The center wavelength movement of fiber grating reflecting is not strictly linear relationship with the measured temperature due to the influence of grating materials, fiber materials, packaging and other factors. This makes the fiber Bragg grating temperature sensor produce error. In order to improve the accuracy of temperature measurement, the more mature method is to use the conic fitting method to correct the error. This method has good temperature measurement accuracy in the medium-low temperature region (-20.0∼80.0°C). But the error of the medium-high temperature region (80.0∼140.0°C) increases gradually. In this paper, the cubic fitting method of wavelength shift is proposed and a temperature measuring device is developed by using this method. The method selects the center wavelength of the reflected light at the temperature of 0° as the reference wavelength and The measured temperature is fitted with the cubic polynomial of the shift Δλ between the reflected wavelength and the reference wavelength. The temperature measurement experiment shows that this method improves the temperature measurement accuracy of the medium-high temperature zone under the premise of calibration in the medium-low temperature zone.