Experimental and mechanistic research on the thermal regeneration of post-hydrogen-loaded drawing tower fiber Bragg gratings

To overcome the stability limitations of conventional drawing tower fiber Bragg gratings (DTGs) at temperatures exceeding 300 °C, this study proposes a novel strategy for fabricating high-temperature resistant gratings through the thermal regeneration of post-hydrogen-loaded DTGs. The regeneration process, regeneration characteristics, and temperature sensing characteristics of these gratings were systematically investigated. Results indicate that the thermal regeneration mechanism of post-hydrogen-loaded DTGs is jointly dominated by chemical composition theory and crystallization theory. Moreover, the continuity between post-hydrogen loading treatment and annealing process significantly affects the regeneration efficiency of the grating. After regeneration at 900 °C, the reflectivity of the regenerated DTG retains 13.8% of the seed grating, which is still exhibiting high-temperature sensing capability at 900 °C with a sensitivity of 16.37 pm/°C. Notably, a Thermo-Hydrogen-Stabilized grating annealed at 600 °C demonstrates high reflectivity comparable to the seed grating, along with excellent temperature sensitivity (14.68 pm/°C). These gratings enable distributed sensing under extremely high-temperature environments and show promising potential for application in high-temperature structural health monitoring.