| 摘要 |
PURPOSE:To obtain optical fiber preform having improved refractive index, by controlling concentration of three or more glass raw material gases having different dopant gas contents and jetting the gases from a burner of multiple pipe. CONSTITUTION:First, dopant bubblers 8a-8d are charged with a proper amount of a dopant such as GeCl4. The dopant is heated to a temperature of about 35 deg.C by a constant temperature device 10 and vaporized by introducing an inert gas such as Ar gas, He gas, etc., from an inert gas feeder. A proper amount of a glass raw material such as SiCl4, etc., put in a bubbler for glass raw material is heated approximately in the same way and vaporized by introducing an inert gas. Each equivalent amount of a glass raw material gas is sent to feed pipes 12a-12d. The flow rate is determined by taking refractive index distribution of optical fiber preform into consideration and regulated by control valves attached to the glass raw material gas feed pipes 12a-12d. |
