PRODUCTION OF GLASS PREFORM

摘要

PROBLEM TO BE SOLVED: To provide a preform for a high-performance optical fiber at a low cost by producing the glass preform which has the center of a core consisting of low-refractive index glass, has a high-refractive index portion on its outer periphery or has a high refractive index at its center and a low-refractive index portion at the outer periphery with simplicity and high efficiency while preventing the infiltration of an OH group into the central core. SOLUTION: The ratio (molar ratio to the total component atoms) of the hydrogen atoms in the gas to be passed to a burner 2 for glass particulate synthesis which successively forms the glass to constitute the high-refractive index portion by an external deposition method on the outer side of a glass rod 1 constituting the center of the core and forms first five layers to be externally deposited at this time is specified to 10 to 24%. The composition of the gas to be passed to the burner for glass particulate synthesis is formed by regulating the flow rate ratio of the gaseous raw material and gaseous hydrogen in such a manner that the gaseous raw material is excessive in the reaction that the gaseous raw material forms silicon oxide by reacting with the gaseous hydrogen and gaseous oxygen.