| 摘要 |
PURPOSE:To manufacture a parent material having an uniform composition in the longitudinal direction whose greater part can be effectively utilized for an optical fiber by changing the time to start the charging of a glass material into each burner in the manufacture of a porous parent material by a VAD process. CONSTITUTION:The raw material is firstly charged only into a burner 10 for the clad, and only an oxyhydrogen flame is passed through burners 9 and 10 to grow the first clad layer 14 on a starting material 12. When the diameter of the first clad layer 14 becomes approximately equal to the diameter of the first clad layer when the shape of an amorphous parent material is stabilized, the raw material is also charged into the burner 9 for the core and only the oxyhydrogen flame is passed through the burner 11. The starting material 12 is pulled upward in accordance with the growth of a core part 13. When the second clad layer 15 can be deposited on the side surface of the first clad layer 14, the raw material is also charged into the burner 11 for the clad. The second clad layer 15 is successively deposited on the first clad layer 14 to manufacture the parent material for an optical fiber. |
