PRODUCTION OF PREFORM FOR OPTICAL FIBER AND APPARATUS THEREFOR

摘要

PURPOSE:To stably and readily produce a preform for optical fibers, by depositing fine glass particles synthesized in a flame in separate reaction vessels and respectively forming a core porous glass body of a small diameter and thick clad porous glass body. CONSTITUTION:Fine glass particles synthesized in a core flame stream 31 of a core torch 24 are adhered and deposited in the axial direction of a starting material 32 to be pulled up in the axial direction while rotated to form a core porous glass body 29 of a small diameter. A thick clad porous glass body layer 34 is similarly formed on the side of the above-mentioned glass body 29. The resultant porous glass body is then heated and sintered at a high temperature and transparentized to give a preform for optical fibers. In the above-mentioned method, the core porous glass body 29 and clad porous glass body layer 34 are respectively formed in the first and second reaction vessels 21 and 22 individually separated by a separating vessel 23. Thereby the core porous glass body 29 of the small diameter is stably formed without any influence of a clad flame stream 33 to afford the aimed preform having a given diameter ratio of the clad layer to the core.