| 摘要 |
PURPOSE:To prevent residual chlorine in a preform for optical fibers, by dehydrating a porous glass preform in a chlorine atmosphere, dechlorinating the preform and transparently vitrifying the preform. CONSTITUTION:A porous glass body formed by aggregating fine glass particles is subjected to dehydration treatment by holding the body in an atmosphere, containing chlorine or a compound thereof and kept at a high temperature or passing through the atmosphere and then transparently vitrified to produce the aimed preform for optical fibers. In the process, the chlorine contained in the porous glass body after the above-mentioned dehydration treatment is reduced to subsequently carry out the transparent vitrification. The dechlorination treatment which is carried out after the above-mentioned dehydration treatment is preferably conducted by heat-treating the porous glass body at 1,000-1,200 deg.C temperature in an atmosphere containing oxygen or a fluorine compound. The transmission and radiation resistance characteristics of the optical fibers are improved by the above-mentioned dechlorination treatment. |
