Optical fibres for high radiation dose environments

A variety of modern single mode (SM) and graded index (GI) fibres as well as a new pure silica multimode step index (MMSI) fibre with high OH content were irradiated at a /sup 60/Co gamma ray source with a dose rate of /spl ap/1.5 Gy/s up to a total dose of 10/sup 6/ Gy. The radiation-induced loss of all fibres was measured continuously during and after irradiation at discrete wave lengths (/spl ap/850, /spl ap/1070, /spl ap/1300, /spl ap/1550 nm). With one SM fibre type also the "breaking stress" before and after irradiation was determined. Radiation-induced losses of /spl lsim/5 dB/50m (at /spl ap/1300 nm) were found with some of the SM fibres, whereas the MMSI fibre showed a final induced loss of only 0.5 dB/50m at 1070 nm wavelength. The breaking stress of the SM fibre increased by about 10%.>