| 摘要 |
PURPOSE:To obtain a sufficiently dehydrated preform having a refractive index distribution effective as a light-transmittion material, by changing the particle size of glass soot forming a porous glass, thereby making a radial distribution in the amount of fluorine added to the glass. CONSTITUTION:A porous glass is maintained in a high-temperature furnace or passed through the furnace to effect the addition of fluorine and the dehydration and clarification of the glass. In the above process, the particle size of the glass soot constituting said porous glass is varied along the radial direction of the porous glass. The amount of the fluorine added to the porous glass in the high-temperature furnace is radially distributed by this method. The means to form a radial distribution of the particle size of the glass soot is e.g. the method to form the glass soot by oxyhydrogen flame, CO flame, plasma flame, or sol-gel process or their combination, under varying conditions. |
