Patent ID: 8701447

Claim:
An apparatus for dehydrating and sintering a porous glass base material for an optical fiber, comprising: a furnace tube which employs a composite tube, the composite tube including a portion formed by jacketing a first quartz glass tube containing aluminum equal to or less than 0.01 ppm with a second quartz glass tube containing aluminum equal to or more than 15 ppm; a gas introducing port that introduces gas into the furnace tube; a gas discharging port that discharges gas from the furnace tube; and a convection preventing plate that is mounted adjacent to a porous glass base material mounting part of a shaft for supporting the porous glass base material, the convection preventing plate having a diameter approximately equal to a diameter of the porous glass base material before being reduced by dehydrating and sintering, wherein the first quartz glass tube which contains aluminum equal to or less than 0.01 ppm includes a synthetic quartz, and the second quartz glass tube is crystallized by preheating.