Abstract

This study investigates the temperature sensitivities of fiber Bragg grating (FBG) across a broad temperature spectrum ranging from −196 ℃ to 900 ℃. We developed the FBG temperature measurement system using a high-temperature tubular furnace and liquid nitrogen to supply consistent high and low temperatures, respectively. Our research showed that the FBG temperature sensitivity changed from 1.55 to 10.61 pm/℃ in the range from −196 ℃ to 25 ℃ when the FBG was packaged with a quartz capillary. In the 25–900 ℃ range, the sensitivity varied from 11.26 to 16.62 pm/℃. Contrary to traditional knowledge, the FBG temperature sensitivity was not constant. This inconsistency primarily stems from the nonlinear shifts in the thermo-optic coefficient and thermal expansion coefficient across this temperature spectrum. The theoretically predicted and experimentally determined temperature sensitivities of FBGs encased in quartz capillary were remarkably consistent. The greatest discrepancy, observed at 25 ℃, was approximately 1.3 pm/℃. Furthermore, it was observed that at 900 ℃, the FBG was rapidly thermally erased, exhibiting variable reflected intensity over time. This study focuses on the advancement of precise temperature measurement techniques in environments that experience wide temperature fluctuations, and has considerable potential application value.

© 2024 Optical Society of Korea