| 摘要 |
PURPOSE:To obtain a base material for homogeneous optical fibers, having good dimensional accuracy and improved reproducibility of refractive index distributions by gelling colloidal silica to make a porous base material and doping metallic ions therein then drying and sintering the base material. CONSTITUTION:Colloidal silica 1 is poured into a glass vessel 2 or the like and the vessel is sealed with a cover 3. The temp. in the vessel is held to allow the silica to gel. The liquid phase content of the gel-like silica is decreased to <=5wt% by providing a fine hole to the cover 3 or the like whereby a porous base material 4 is obtained. The material 4 is immersed in a dopant soln. 6 which is an aq. phosphoric acid soln. or the like in a diffusing tank 5 and is heated to dope metallic ions therein. The base material is taken in an silica tube etc. and heated, dried while gaseous oxygen, etc. is flowed. Then gaseous chlorine is flowed to cause dehydroxylating reaction and further gaseous He or the like is fed to sinter the base material by heating, whereby the optical fiber base material is obtained as a transparent glass body. |
