X-Ray, Proton, and Electron Radiation Effects on Type I Fiber Bragg Gratings

Fiber Bragg gratings (FBGs) are one of the most used optical fiber sensors and they have recently drawn the attention of several research groups for their potential applications in harsh radiation environments. Up to now, their performances have been mainly evaluated under ionizing radiations, such as X-rays or $\gamma $ -rays. We compare here the effects of different irradiation types, including X-rays, protons, and electrons, on type I FBGs written by UV laser exposure in Ge-, P/Ce-, and B/Ge-doped single-mode optical fibers. Different irradiation conditions were used according to the sources; 6-MeV electron irradiations were performed at a dose rate of 120 Gy(SiO 2 )/s up to an accumulated dose of 500 kGy; whereas for the 63-MeV protons, the estimated equivalent dose rate was of 0.75 Gy(SiO 2 )/s up to a total dose of 7 kGy. In order to compare their effects with those induced by X-rays, two irradiations with 45-keV photons were performed with different dose rates [0.75 and 60 Gy/s (SiO 2 )] up to a total dose of 10 and 500 kGy, respectively. We demonstrated that X-rays and protons induce comparable effects at doses of about 10 kGy, whereas the behavior under electron beam appears to be strongly dependent on the fiber composition. For example, the grating in the B/Ge co-doped fiber is the most sensitive to electrons and the most resistant to X-rays; whereas the FBG inscribed in the H 2 -loaded P/Ce co-doped fiber has exactly the opposite behavior.