| 摘要 |
PURPOSE:To obtain the titled glass having a uniform dopant concentration, by exposing a porous glass material consisting of SiO2 to a gas for forming a doped silica glass, forming an SiO2-dopant solid solution, the making the solid solution into a transparent glass. CONSTITUTION:A quartz glass tube 31 is heated by a flame 33 while being rotated, and a raw material gas for forming glass is made to flow through the glass tube 31 and form a porous glass layer 32 on the inner wall of the glass tube 31. The internal temperature of the glass tube 31 is then reduced to 500-1,000 deg.C, and a gaseous additive, e.g. GeCl4 or POCl3, capable of forming a solid solution on reaction with water and a gas for forming doped silica glass consisting of steam essentially are introduced into the glass tube 31 to form an SiO2-dopant solid solution on the surface of the porous glass layer 32. The resultant porous glass layer 32 is then made into a transparent glass and form a doped silica glass layer 34, and the layers 31 and 32 are collapsed to give a base material for an optical fiber. |
