| 摘要 |
<p>An object of the present invention is to provide a method for producing a favorable optical fiber preform at a low cost, which comprises favorably changing from a gas supply state to a reduced pressure state, and thereby acquiring a long effective length of the quartz glass tube. The above problems are solved by a method for producing an optical fiber preform comprising inserting a core glass rod for use in the optical fiber preform into the quartz glass tube for the optical fiber preform and then welding them in a heating furnace for melt welding them together into a monolithic product, characterized in that the melting is started in such a state that the lower open edge of said quartz glass tube is placed inside the heating furnace and a gas is supplied from the upper edge of the tube, and after the lower edge portion of the quartz glass tube is drawn out from said heating furnace by melt deformation and stretching by the gravitational force, the gas supply is cut off and the pressure is reduced.</p> |
