Loss increase due to hydroxyl group formation of a fiber expose to hydrogen gas in measured. Experimental result shows that the loss increase is proportional to 0.57 power of exposure time. Temperature dependence of the loss increase is also estimated from the result.

Phenomenon of silica-fiber loss increase, which is induced by an electric current applied in water, is reported. It is found from experimental results that the loss increase is caused by hydrogen molecules, which are electrolytically produced and are diffused into the fiber interstitially. Furthermore, both infrared loss and Ramanscattering spectra are measured for a fiber dissolved by H2, HD, and D2 molecules to make clear assignment for loss peak. As a result, it is found that the absorption loss peaks are associated with a connection between molecular vibration and SiO4 tetrahedral vibrations in the silica glass.

Optical fiber cable systems are being developed in many countries for subscriber loops as the infrastructure to realize B-ISDN (Broadband Integrated Services Digital Network). The present systems are DLC (Digital Loop Carrier) systems which provide leased lines, POTS (Plain Old Telephone Services), and N-ISDN (Narrowband ISDN) services. Before FTTH (Fiber To The Home) networks can be implemented, their construction cost must be lowered to the level of the current metallic network. The FTTH network must also be easy to operate and maintain. In this paper, we describe optical fiber cables, splicing, and testing technologies used in the NTT cable networks, and introduce the technologies being developed to construct FTTH networks.