| 摘要 |
PURPOSE:At the start of clear glass formation, the starting material is changed from in pulled-up state to in pulled-down state to keep the growing surface of the porous parental material at a constant position to avoid axis deviation. CONSTITUTION:After the porous parental material 3 is made to grow up to the top of the heater 7, as it is pulled up, the pulling-up is stopped to heat the parental material 3 by the heater 7 to effect rapid shrinkage so that a part of the parental material 3 remains between the starting material 5 and the shrinking part and the rotation center of the clear glass part of the parental material 3 is allowed to coincide with the rotation center of the growing surface of the material 3. Then, the starting material is kept in pulling-down state, a part of the parental material 3 remaining at the top end of the starting material 5 is made completely clear to cause shrinkage only on the boundary surface between the optical fiber material 4 and the parental material 3, then the starting material is shifted to in the pulling-down state. Thus, the growing surface of the porous parental material is kept constant whereby optical fiber with little fluctuation is obtained without deterioration in band characteristics. |
