| 摘要 |
PURPOSE:To prepare a parent material of optical fiber contg. no impurities and having low transmission loss by heating a porous parent material for optical fiber in a quartz muffle tube in a heating furnace while flowing dehydrating gas, and dehydrating the parent material and then sintering. CONSTITUTION:A quartz muffle tube 5 attached with quartz tubes 6, 8 to the top end and the bottom end is installed in a heating furnace 3 provided with a carbon heater 4, in which a porous parent material 1 deposited to the top end on a bar-shaped base material 2 is inserted. Dehydrating gas comprising gaseous chlorine diluted with He or gasous inorg. chlorine compd. such as SOCl2, etc. is introduced from a feeding port 8 of the dehydrating gas, and dehydration is performed by heating the parent material 1 at a temp. capable of maintaing the porous state of the parent material. Then, the temp. of inside of the furnace is elevated in the same atmosphere to perfrm sintering of the parent material 1. By this method, mixing of impurities such as OH is prevented, and a transparent vitrified parent material for optical fiber having low transmission loss is obtd. |
