Hydrogen Permeation in Hermetically Coated Optical Fibers

The use of hermetic coatings on optical fibers can prevent strength degradation caused by the presence of H sub 2 O at the fiber surface and can also prevent loss increases that might arise from H sub 2 in the fiber environment. Recent reports have discussed the properties attained using amorphous carbon coating on single mode fibers. Fibers coated in such a fashion have shown improved resistance to fatigue, as indicated by the high "n" values obtained in static and dynamic fatigue experiments. Presumably the tightly packed carbon structure is capable of physically blocking the diffusion of water molecules from the environment to the silica surface.