Radiation-Induced Attenuation in Single-Mode Phosphosilicate Optical Fibers for Radiation Detection

We investigated the online radiation-induced attenuation of two single-mode optical fibers (OFs) that were X-rays irradiated with doses up to 100 kGy(SiO₂) at room temperature at 10.7 Gy/s. One of the two samples was doped only with phosphorous, whereas the other was codoped with phosphorous and cerium. Both OF types are very radiation sensitive in the near-infrared (NIR) domain and of interest for applications involving radiation detection. The addition of Ce to the P-doped core lowers the radiation sensitivity of the OF and introduces a spontaneous postirradiation recovery process at room temperature, which is negligible in the purely P-doped OF. We show that the diffusion of molecular hydrogen into the OFs allows the full recovery of the NIR losses caused by radiation-induced P-related point defects. However, the radiation response of the H₂-regenarated samples is substantially different from that of the pristine ones. We conclude that the H₂-loading procedure cannot be at the moment considered as a valid technique for the regeneration of a depleted P-doped OF radiation sensor.