Fig. 1. Change in the reflectivity of femtosecond FBG at an annealing temperature of 1000 ºC

Fig. 2. Change in the resonant wavelength of femtosecond FBG at an annealing temperature of 1000 ºC

Fig. 3. Diagram structure of tube packaged femtosecond FBG high temperature sensor

Fig. 4. Temperature cycling of 4 femtosecond FBG high temperature sensors with different initial wavelengths. (a) 1530 nm; (b) 1535 nm; (c) 1540 nm; (d) 1545 nm

Fig. 5. Quasi-distributed temperature measurement application of cylindrical high temperature components based on femtosecond fiber grating high temperature sensor

Fig. 6. Measured temperature distribution of three different parts of cylinder samples.（a）Top part；（b）middle part；（c）bottom part