Mechanical and chemical characteristics of hermetically coated silica optical fibre

The mechanical strength of carbon hermetically coated fibres, compared to standard single mode silica optical fibre, has been investigated through chemical exposure to fluorinated vapour reagents, known as the harshest reagents for silica. Two reagents were used: ammonium hydrogenofluoride and hydrofluoric acid. c fatigue tests for different stress rates were implemented using a two-point bending testing device in order to determine n-stress corrosion parameter from Weibull statistics. As-received and chemically etched fibres were compared. ically coated fibres appeared extremely durable in harsh chemical conditions. No significant change in the Weibull distribution and the mean fibre strength was observed after 6 days of chemical exposure to hydrofluoric vapours. In the same conditions, the mechanical strength of the epoxy-acrylate polymer coated standard fibres has decreased to nearly 50% of the initial strength value. SEM observations revealed crystal deposition on the chemical exposed fibres. Chemical analysis provides partial information on the complex mechanisms of fibre corrosion.