| 摘要 |
PURPOSE:To contrive to improve the adhesion yield of glass fine particles by depositing glass fine particles on a heat resistant starting material in the axial direction thereof by a VAD method, allowing the glass fine particle deposition to grow and forming the bottom shape of the grown deposition in the downwardly depressed shape to prepare a porous glass base material. CONSTITUTION:A heat-resistant starting material such as quartz glass is suspended from a rotating lifting device in a reaction vessel, and a mixture of a Si compound such as SiCl4 using O2 gas as a carrier gas with a GeCl4 dopant using O2 gas as a carrier gas, H2 gas and O2 gas as combustion gases are fed into an oxygen hydrogen flame burner. The temperature distribution of the flame of the oxygen hydrogen flame burner is controlled so as to be high at the central portion thereof and be wide, and the produced glass fine particles are deposited or the starting material, followed by lifting the starting material in the axial direction to prepare a porous glass base material having a downwardly deposited bottom shape. The porous glass base material is sintered at 1400-1450 deg.C to form a transparent glass, thereby providingan optical fiber base material. |
