| 摘要 |
PURPOSE:To obtain preform for optical fiber having small transmission loss, by inserting a rod for core comprising SiO2 glass into a hallow part of a specific pipe for clad and heating the pipe using hydrogen-containing flame as a heating source. CONSTITUTION:In production of perform for optical fiber by inserting a rod for core comprising SiO2 glass into a pipe for clad having difference in specific refractive index >=0.5 smaller than that of the SiO2 glass and heating to fuse and to integrate both the rod and the pipe, a fluorine-containing SiO2 glass pipe having <=50mm outer diameter is used as the pipe for the clad, hydrogen- containing flame is used as a heating source in heating and the core diameter A and the clad diameter B after fusing and integration are made to satisfy conditions of A>=2mm, B/A>=6 and 1/2(B-A)>=7mm. H2/O2 flame or hydrocarbon/O2 flame such as natural gas/O2 flame, methane/O2 and propane/O2 are preferable as the hydrogen-containing flame with respect to supply of easy flame with strong heating power. |
