MANUFACTURE OF OPTICAL FIBER PREFORM

摘要

PURPOSE:To obtain an optical fiber preform having excellent polarization maintaining property, by using a torch to synthesize a porous preform and another torch for producing a clad, and periodically varying the dopant concentration of the glass raw material supplied to the clad torch. CONSTITUTION:An axially extending porous preform rod 21 is produced by using the torch 26 for synthesizing porous preform. The dopant concentration in the vapor of glass raw material supplied to the other torch 28 for cladding is varied periodically according to the rotation of the preform 21. The glass soot layer 33 is deposited to the side surface of the preform 21 using the torch 28. The product is heated and sintered at a high temperature to obtain a clear preform.