X-ray irradiation effects on fluorine-doped germanosilicate optical fibers

We report an experimental investigation on the effects offluorine codoping on the radiation response of Ge-doped Optical Fibers(OFs) obtained by three different drawing conditions. The OFs wereirradiated with 10 keV X-rays up to 300 Mrad and studied by onlineRadiation-Induced-Attenuation (RIA) measurements. Confocal Micro-Luminescence (CML) and Electron Paramagnetic Resonance (EPR) werealso employed to investigate the permanent radiation-induced-defects. Thevariation of the Germanium-Lone-Pair-Center (GLPC) and Non-Bridging-Oxygen-Hole-Centers (NBOHC) concentration with the radiation dose isinvestigated by CML, whereas the ones of the induced Ge(1), Ge(2) and Eʹcenters by EPR. No relevant differences are found in the RIA of the threefibers, as well as in the induced concentrations of Ge(1) and Ge(2) and inthe decrease of the GLPC, showing minor relevance of changing thedrawing conditions. We found that fluorine codoping does not affect theRIA and that, unexpectedly, the fluorine co-doped zones of the OFs showan enhanced photoluminescence of the radiation induced NBOHC enablingto suggest the presence of both Si and Ge variants. Moreover, an overallincrease of the radiation induced Eʹ(Ge) centers is registered in relation tothe presence of fluorine showing that this codopant has relevant effects.