Radiation Resistance of Er-Doped Silica Fibers: Effect of Host Glass Composition

With the aim to find the best-suited host glass for radiation-resistant erbium-doped fibers (EDF), radiation-induced absorption (RIA) is measured and analyzed after γ -irradiation to 3.0-4.5 kGy in 18 silica optical fibers with various concentrations of dopants: Al₂O₃ , P₂O₅ , GeO₂ and Er₂O₃ . The RIA dependence on the content of Al₂O₃, P₂O₅ and Er₂O₃ in singly doped fibers is investigated. RIA of fibers codoped simultaneously with Al₂O₃ and P₂O₅ are found to be significantly lower than those of singly Al₂O₃ -doped fibers. This is explained as the result of the formation of AlPO₄-joins in the silica network. GeO₂ codoping of AlPO₄ -doped silica is shown to further reduce RIA. Nevertheless, the application of H₂ -loading and photobleaching of RIA by 980-nm laser radiation shows that the AlPO₄ - and GeO₂ -codoped silica is outperformed by P-free Al₂O₃- and GeO₂-codoped silica, which is, therefore, concluded to be the best host glass composition for radiation resistant EDFs.