| 摘要 |
PURPOSE:To obtain a base material for single mode optical fibers with low loss without exhibiting light absorption of OH groups, by synthesizing a porous glass on the surface of a cylindrical core base material with a flame without producing H2O, and heat-treating the porous glass to give transparent glass. CONSTITUTION:Fine SiO2 glass particles, together with a flame without producing H2O, are blown from a burner 3 made of quartz glass on a cylindrical core base material 1 preformed by the vapor phase axial deposition (VAD) method, etc. while rotating the cylindrical core base material 1 to deposit the fine particles thereon, and a porous glass layer 4 is formed. A flame obtained from CO- O2, CO-Cl2 or CO-O2-Cl2 gas is perferably used as the flame without producing H2O. The whole base material consisting of the core base material 1 and the porous layer 4 is then dehydrated under heating in a Cl2 atmosphere, etc. in an electric furnace and then heat-treated in a helium atmosphere, etc. containing fluorine, etc. to give transparent glass and give the aimed base material for single mode optical fibers. |
