EPR investigation of the radiation response of different types of germanosilicate optical fibers

In this study, we investigate through Electron Paramagnetic Resonance (EPR) measurements the radiation response of a set of multimode Telecom-grade optical fibers (OF) responding to the standards of ISO/IEC. The doping levels of these germanium-doped OFs have been adjusted to optimize their bandwidth and loss levels through controlling their refractive index profiles. The purpose of this paper is to understand if the modification of the manufacturing process changed their radiation response, through the radiation induced point defects. We irradiated those fiber samples with different types of particles (X, ɣ and e-) reaching different doses and dose rates. EPR spectroscopy was exploited to track the evolution of paramagnetic Ge-related point defects such as Ge(1), Ge(2), E'Ge and E'Si. Our results show that the concentrations of these defects do not depend drastically on the fiber type, suggesting that the applied changes in the manufacturing process have minor impact on their generation efficiencies under irradiation. However, we note a detectable difference of E'Ge induced concentration in one of the fibers up to a 45 %. This can be explained by the fact that there is a greater concentration of strain bonds in the silica network.