MANUFACTURE OF OPTICAL FIBER PREFORM

摘要

PURPOSE:To obtain a preform for low-loss single-mode optical fiber having excellent polarization maintaining property, by depositing glass soot to the circumference of a glass rod core while periodically varying the dopant concentration in the raw material gas synchronously with the rotation of the rod. CONSTITUTION:Glass soot is deposited to the circumference of the rotating glass rod 21 for core or having a core-clad structure by the flame hydrolysis using the torch 24 for synthesizing glass soot. The concentration of dopant (GeCl4, POCl4, TiCl4 or BBr3) in the raw material gas (SiCl4 and the dopant) supplied to the torch 24 is varied periodically and synchronously with the rotation of the rod 21. After forming a porous glass layer to the circumference of the glass rod 21, it is heated and sintered at a high temperature to obtain the objective preform.