| 摘要 |
PURPOSE:In the production of preform for optical fiber by the VAD method, the bottom temperature of the core in the soot material is detected and the core burner is allowed to move in the perpendicular direction so that the detection temperature is kept constant whereby optical fiber with uniform difference in specific refractivity in the lengthwise direction and reduced transmission loss is obtained. CONSTITUTION:The raw materials for the core glass are fed from the core burner 1, while the those for the clad glass are fed from the clad burner 2 to the target, respectively. At the same time, the individual materials are hydrolyzed with oxyhydrogen flame to form the soot material 3 while is composed of the core part 31 and the clad 32 wrapping the core part 31 on the tope end of the target. Then, the soot materials 3 are clarified to give the preform for optical fiber. In the production of the above-stated soot material 3, the bottom temperature T of the core 31 is detected and the core burner 1 is allowed to move vertically depending upon the change in the bottom temperature T so that it is kept at a prescribed value constantly. |
