| 摘要 |
PURPOSE:To obtain a base material having a highly controlled outside diameter and suitable for use in the manufacture of an optical fiber by spinning by drawing a perpendicularly fixed rodlike or tubular glass material upward while successively heating the material from the upper part toward the lower part. CONSTITUTION:A rodlike or tubular transparent quartz glass material formed from porous glass or the like is perpendicularly fixed by attaching both ends of the material 1 to a chuck mechanism, and the material 1 is drawn upward while moving a heated part from the upper end toward the lower end. For example, a heating source 3 such as a burner, an electric resistance furnace or a high frequency electric furnace is fixed, and the material 1 is drawn upward while moving the material 1 itself upward. When the material 1 is drawn, relation represented by an equation V1.phi1<2>=V2.phi2<2> is established. In the equiation, phi1 is the outside diameter of the material 1, V1 is the moving speed, V2 is the drawing speed, and phi2 is the outside diameter after drawing. The material 1 can be drawn to the desired outside diameter phi2 according to the equation. A sagged part 3' is formed during drawing.
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