| 摘要 |
PURPOSE:To improve the quality by introducing the open air into a chamber of an inner pipe in a state isolated from the outside of a reactional chamber and guiding a corrosive gas and residual soot produced in depositing a core soot into a gas discharge duct. CONSTITUTION:A glass raw material SiCl4 and a doping raw material GeCl4 are fed into a torch 2 and a flame 4 containing glass fine particles is then jetted toward a seed rod 3. An SiO2 core soot 5 is subsequently deposited and grown on the tip of the glass seed rod 3 moving in the direction of an arrow (B) under rotating. A corrosive gas and residual soot produced at this time are guided to an inner pipe 20 of a gas discharge duct 10. When the gas discharging capacity of the gas discharge duct 10 exceeds the amounts of the corrosive gas and the residual soot, the open air introduced from suction ports 36 and 37 is sucked into a chamber of the inner pipe. Thereby, uncontaminated air in a reactional chamber 1 neither flows into the interior of the gas discharge duct 10 nor produces turbulence. The resultant formed porous glass body is thermally dehydrated with a high-temperature gas and transparentized to afford the objective high-quality optical fiber preform without any difference in outside diameter and refractive index and micro-fluctuation in refractive index (R1) distribution in the longitudinal direction. |
