Silica optical fibre behaviour to chemical exposure to hydrofluoric acid vapours

International audienceReliability of standard single mode silica optical fibre and hermetic coated fibre has been investigated through chemical exposure to hydrofluoric acid (HF) vapours into a hermetic closed disposal for different durations. Dynamic fatigue tests were implemented using a two-point bending testing device. Three series of samples subject to HF attack for variable times were compared. Standard fibres tested immediately after exposure show a broader distribution of fibre strength accompanied by the drastic decrease of the failure stress. Drying treated standard fibres prior to testing has also led to a broader distribution and a slight decrease of failure stress by comparison to as-received fibres. Drying in oven prior to mechanical measurement makes handling difficult and results in brittle fibres that exhibit much lower strength and broader distribution of failure stress. Polymer reacts with hydrogen fluoride, which induces viscosity changes, but it returns to solid state after thermal treatment. This is consistent with SEM observations. Same experiments have been implemented on the hermetic coated fibre. No significant change in the Weibull distribution and the mean fibre strength was observed after 6 days of chemical exposure to HF vapours. By comparison to standard commercial fibre, the hermetic coated fibre appeared extremely durable in harsh chemical conditions