The degradation in tensile strength of polymer-coated glass optical fibres under γ-irradiation

The tensile strength of glass optical fibres when coated with various polymers has been measured as a function of γ-ray dose. Fibres protected with acrylate, silicone + acrylate or polyimide coatings showed little degradation after receiving a total dose of 1 MGy (they retained > 95% of their preirradiated strength). For a fibre with an extruded nylon overcoat the nylon became very brittle after 0.5 MGy, but as far as could be assessed, the strength of the central glass fibre was little affected. Two other types of fibre, both protected with fluorinated polymers, were severely weakened after 0.1 MGy (their tensile strength being reduced to < 40% of their pre-irradiated strength). Experimental results are given supporting the hypothesis that the degradation results from gaseous fluorine-containing species chemically attacking the surface of glass fibre. (Author)