Effect of photobleaching on radiation-induced transmission loss of fused-silica-core optical fibres under gamma-ray and 14 MeV neutron irradiation

摘要

The effect of photobleaching on radiation-induced transmission loss of fused-silica-core optical fibres was examined under ~(60)Co gamma-ray and 14 MeV neutron irradiation. In the visible wavelength range, the radiation-induced transmission loss could be reduced by photobleaching under both types of irradiation. It is considered that the number of radiation-induced defects such as E' centre and NBOHC that cause optical absorption was reduced by photobleaching. For using optical fibres in the visible wavelength range as light guides or image guides, photobleaching is an effective technique to improve their radiation resistance. However, a so-called microbending loss is induced by radiation in the entire wavelength range. The loss response to photobleaching was different under gamma-ray and fast-neutron irradiation. The loss under the gamma-ray irradiation increased due to photobleaching, while that under the fast-neutron irradiation decreased. It is considered that there are multiple reasons for the radiation-enhanced microbending loss. In general, it is concluded that the photobleaching technique is effective in improving the radiation resistance of fused-silica-core optical fibres under neutron and moderate flux radiation environments.