Application of diamond-like carbon films as hermetic coatings on optical fibres

Abstract

The application of diamond-like carbon (DLC) films as hermetic coatings on optical fibres was investigated. Films with refractive indices in the range 1.7-2.0 (at λ = 675 nm) were deposited at pressures up to 5 Torr. The hermeticity of the coatings was determined using water penetration studies monitored using a combination of spectroscopic ellipsometry and atomic force microscopy. The resistance to moisture penetration was found to be better for higher refractive index films. The coatings were applied to optical fibres in a continuous in-line system as the fibre was drawn. Coatings of thicknesses in the range of 10–30 nm were achieved on quartz fibres with outer diameters of 200–1000 μm at fibre drawing speeds of up to 3 m min−1.