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: Al
₂
O
₃
, P
₂
O
₅
, GeO
₂
and Er
₂
O
₃
. The RIA dependence on the content of Al
₂
O
₃
, P
₂
O
₅
and Er
₂
O
₃
in singly doped fibers is investigated. RIA of fibers codoped simultaneously with Al
₂
O
₃
and P
₂
O
₅
are found to be significantly lower than those of singly Al
₂
O
₃
-doped fibers. This is explained as the result of the formation of AlPO
₄
-joins in the silica network. GeO
₂
codoping of AlPO
₄
-doped silica is shown to further reduce RIA. Nevertheless, the application of H
₂
-loading and photobleaching of RIA by 980-nm laser radiation shows that the AlPO
₄
- and GeO
₂
-codoped silica is outperformed by P-free Al
₂
O
₃
- and GeO
₂
-codoped silica, which is, therefore, concluded to be the best host glass composition for radiation resistant EDFs.