Radiation-induced-defects localization in single-mode optical fibers

We studied the defects at the origins of the permanent radiation-induced attenuation in four gamma-rays irradiated single-mode germanosilicate optical fibers (similar to 1 MeV; 1.2 kGy; 0.3 Gy/s) in the 14 spectral range 400 - 1700 nm. We determined the wavelength dependence of the following cladding codopant influences: germanium (0.3 %), phosphorus (0.3 %), fluorine (0.3 %) on the germanosilicate (13 %) fiber radiation responses. We identified some of the different color centers produced by gamma-rays and we evaluated their localization in the fiber cross-section through the determination of the radial distribution of the radiation-induced absorption at 633 nm. We also evidenced the strong interactions between these three codopants. In particular, our results showed that the properties of the phosphorus-related color centers, which mainly determine the fiber infrared radiation sensitivity, are strongly influenced by the germanium- and fluorine-codoping.