| 摘要 |
PURPOSE:In the production of a parent material for optical fiber through the VAD process, the sintering is carried out in a specific gas atmosphere to form the parent material with less deviation in refractive index distribution. CONSTITUTION:In the reaction vessel 30, starting gas materials are burnt with the burner 31 and the resultant glass fine particles are deposited on the starting material 32 which is being pulled up under rotation to form the fine particle aggregate 36 (its bulk density is about 0.1-0.5g/cm<3> and the refractive index is lower in the outer part than in the core part). Then, the aggregate is sintered with the heater 33 in the course of pulling-up to give the objective parent material for glass fiber wherein the sintering is carried out in such a gas atmosphere as containing halogen or a halogen compound and effecting dehydration and dopant vaporization, e.g., a helium gas containing about 0.1-10mol% of molecular chlorine. |
