Gamma-ray irradiation effect on loss increase of single mode optical fibers, 2

In order to examine the reliability of optical fiber systems in nuclear power plants, we estimated the induced losses of pure silica core and GeO2 added core single mode optical fibers (Si-SMF and Ge-SMF) exposed over a long period to low dose rate γ-rays (less than 100R/h, 40yt). Also γ-ray induced losses under a high dose rate and high temperature condition such as 106R/h and 200degC were estimated in view of an accident. In both cases, the induced losses were concluded to depend mainly on total dose from the results of low dose rate irradiation experiments and a study on temperature dependences of induced losses. It was ascertained from the estimation that the Si-SMF had loss radiation sensitivity than the Ge-SMF in the radiation environment of nuclear power plants. The induced loss of the Si-SMF exposed for 40yr to 1R/h γ-rays was estimated to be about 2dB/km and almost five times lower than that of the Ge-SMF. (author)