PRODUCTION OF PREFORM FOR OPTICAL FIBER

摘要

PURPOSE:To easily produce an optical fiber preform having high F content, by separating the process for the generation and deposition of glass soot from the process for the addition of F in the production of a quartz-based optical fiber preform containing F using an inner deposition CVD process. CONSTITUTION:A starting glass tube 11 is externally heated with a moving heat source 12 while passing a gas containing a glass raw material gas (e.g. SiCl4) and O2 gas through the glass tube 11 from an end. Fine powder of SiO2 is deposited on the inner face of the glass tube 11 at the gas-discharging side based on the heat source 12 to form an SiO2 soot layer 13. F is added to the SiO2 soot layer 13 and the SiO2 soot layer 13 is converted to transparent glass by externally heating the glass tube with a moving heat source 12 while passing an F-containing gas (e.g. SiF4) through the hollow part of the glass tube 11. The objective optical fiber preform is produced by collapsing the glass tube having an F-containing SiO2 glass layer 14 on its inner surface.