| 摘要 |
<p>PURPOSE:To produce a parent material for optical fiber resulting low optical loss with high productivity by cooling a hollow part of a cylindrical porous glass parent material with gas, adding fluorine to the glass by holding the external periphery of the material in an F-contg. atmosphere at high temp., and vitrifying the product to transparent glass thereafter. CONSTITUTION:Raw material gas such as SiCl4 is subjected to flame hydrolysis, and generated fine glass powder is deposited to the circumference of a slender starting rod. The rod is ten removed and a cylindrical porous glas parent material 3 is produced. Further, cooling gas 1 contg. no fluorine is flowed through the central hollow part 4 of the parent material 3, and the external periphery of the parent material 3 is held in F-contg. atmosphere 2 (e.g. SF6) at high temp. to cause the reaction shown by the equation. Thus, fluorine is added to the glass providing a gradient of added fluorine content in the radial direction of the parent material 3. Succeedingly, the glass is held in a second atmosphere at higher temp. than the first F-contg. atmosphere 2 to convert the material to transparent glass. Thus, the target parent material for optical fiber is obtd.</p> |
