Interfacial phenomena in optical fibre embedded systems

Abstract

The reliability and the expected lifetime of optical fibres used in different structural applications, including composites are closely related to the chemical environment action on the silica cladding. To ensure the long-term mechanical strength of the optical fibres, a polymer coating was applied onto the fibre surface during fabrication. The aging mechanism is assumed to enlarge or to extend the "Griffith flaws" which are spread at the fibre surface. Systematic experiments have been carried out to assess different reagents' effect on the fibre mechanical strength, such as fluorinated vapors, acetylene, ammonia and organic compounds. Different types of fibres, including hermetically coated ones, have been aged and subjected to mechanical tests under dynamic conditions. The Weibull statistical study allows to evaluate the flaws' dispersion along the fibre surface. SEM observations evidenced several failure mechanisms.