| 摘要 |
PURPOSE:To make it possible to control the refractive index distribution in the stage of an oxide powder rod, by the action of an atmosphere capable of consuming SiO2 on an SiO2-based oxide powder rod, containing GeO2, etc., and prepared by the VAD method. CONSTITUTION:An oxide powder rod 5 containing SiO2 as a principal component and GeO2 alone or another component as a component for forming the refractive index difference is provided in a reaction vessel 1 in a rotated state. On the other hand, O2 is blown into a solution containing F, e.g. HF, in a bubbling container 4, and an atmosphere, unreactive to GeO2, and capable of consuming SiO2 chemically is fed into the vessel 1. The atmospheric gas is permeated from the outer periphery into the rod 5 to consume SiO2 in the rod 5. The GeO2 concentration in the rod 5 is relatively increased to adjust the refractive index distribution in a desired state. In the process, O2 can be supplied from an auxiliary pipe 11 to adjust the atmospheric gas concentration. |
