Diffusion of hydrogen molecules in fluorine-doped single-mode fibres

Permeability of hydrogen molecules into core parts of silica optical fibres is found to be dependent on the glass compositions of cladding parts and hydrogen partial pressure around the fibres. Fluorine doping into silica glasses somewhat increases the diffusion coefficients of hydrogen, and the los increases due to hydrogen molecules in fluorine-doped fibres could be observed sooner than in standard fibres, provided small amounts of hydrogen are generated in optical cables.