Aging of Fiber Bragg Gratings to Reduce the Drift of the Sensor Response on Their Basis at High Temperatures

The paper presents the results of an experimental study of the phenomenon of the resonant wavelength drift of a fiber Bragg grating (FBG) recorded in a hydrogenated germanate quartz optical fiber under stationary action of an increased (+ 100 °C) temperature for a long time. The authors have shown that for FBG that did not undergo preliminary aging at a temperature higher than the operating temperature, the drift of the central wavelength after the first heating cycle lasting 2.5 hours at a temperature of + 100 °C was 80 pm, which corresponds to a change in the temperature sensor response of ~ 6 ° C. To reduce the detected drift, the authors selected the FBG aging modes (temperature and cycle duration), which ensure a decrease in drift to values, that do not exceed the error of a commercial interrogation device used in the course of experiments at a constant elevated temperature for 24 hours.