Radiation effects of 14-MeV fusion neutrons on optical transmission properties of fused silica core optical fibers

Optical transmission properties of optical fibers with a purified and undoped fused-silica core were investigated under irradiation by 14 MeV fast neutrons in the temperature range from room temperature to 573 K at a fast neutron irradiation facility of Fast Neutron Source (FNS). Growth of optical absorption in the wavelength range of 420-630 nm, which includes a well-known absorption peak called Non-Bridging-Oxygen-Hole-Center (NBOHC), took place due to the neutron irradiations. Change of the optical absorption depended strongly on the irradiation temperature. Particularly, growth rate of the radiation-induced optical absorption at the wavelength of 630 nm decreased with increase of the irradiation temperature up to 473 K, because of the dynamic recovery of the initial structural imperfections and the radiation-induced defects.