| 摘要 |
PURPOSE:To uniformalize a refractive index distribution in an axial direction of the preform. CONSTITUTION:The angle and position of burners 1, 2 are so controlled that the gradient of the dopant concn. distribution for increasing the refractive index changes from steeply to gently and slowly in the axial direction of a porous glass particulate deposit 9 at the time of forming the above-mentioned glass particulate deposit by forming glass particulates by a vapor phase chemical reaction in the oxyhydrogen flames of the burners and depositing the glass particulates. This glass particulate deposit 9 is thereafter heated first from the side where the dopant concn. distribution gradient is gentle by using an inclined furnace so as to move the heated section gradually toward the side where the gradient is steep, by which the stage for removing water is executed. Further, a vitrifying stage to transparent glass is executed. |
