| 摘要 |
PURPOSE:To obtain an optical fiber cable having small transmission loss by forming a molten tetrafluoroethylene/ethylene copolymer by extrusion coating at a specific draw- down ratio or below on the outside circumference of an optical fiber strand and cooling quickly the fiber thereby suppressing the molding shrinkage of the copolymer. CONSTITUTION:A cushion layer 4 consisting of a silicone resin, urethane acrylate resin, etc. is provided on the outside circumference of an optical fiber strand 1 consisting of a core 2 and a clad 3 in producing an optical fiber having excellent fire retardance and heat resistance for a nuclear reactor, etc. The melt 5 of a tetrafluoroethylene/ ethylene copolymer (Daikin Kogyo ''Neofron E'', etc.) is extruded and coated at <=20 draw-down ratio on the outside circumference of the layer 4 and is quickly cooled by bringing the same into contact with cooling water (ordinary water of about 20 deg.C) within one second. The molding shrinkage of the above-described copolymer having high crystallinity and high density is thus suppressed and the transmission loss of an optical fiber 1 is minimized. The cable having high reliability is thus obtd. An equally good result is obtd. by assembling the plural strands around a steel wire 6 and forming a sheath 8 consisting of the above-described copolymer on the outside thereof so as to leave a space 7. |
