Hydroxyl production in optical fibres coated with hydrogen-free plastic materials

Optical loss increase characteristics with heat treatment are investigated for two kinds of GeO2-doped silica fibres. The two fibres are coated with polypropylene (PP) and tetrafluoroethylene-hexafluoropropylene copolymer (FEP), respectively. Loss increase due to OH ions occurs through heat treatment for the two kinds of fibres below 500°C, although the thermoplastic materials (PP and FEP) generate no hydrogen gas. It is concluded from the experiments that some origin of hydrogen exists in the fibre glass.