Method of fabricating optical fiber preform

摘要

A method of fabricating an optical fiber preform that can give stable and high deposition efficiency from the start to the end of the deposition when synthesizing a large size preform. When fabricating a preform by hydrolyzing a glass raw material gas in flame to generate glass particles and depositing the glass particles on a rotating starting material in the radial direction using a burner with a concentric multiple-tube structure having at least a plurality of small diameter combustion assisting gas-ejecting ports having the same focal length. L1 is made greater than L2 (L1>L2) during an early stage of deposition and L2 is increased in the course of the deposition so that L2 is greater than L1 (L1

主权项

1. A method of fabricating an optical fiber preform, comprising:
using a burner having a concentric multiple-tube structure and having at least a glass raw material gas-ejecting port arranged at the center of the burner, a flammable gas ejecting port arranged outside the glass raw material gas-ejecting port, and a plurality of small diameter combustion assisting gas-ejecting ports arranged inside the flammable gas-ejecting port in at least one line on concentric circles relative to the glass raw material gas-ejecting port, the plurality of small diameter combustion assisting gas-ejecting ports arranged on the same line having the same focal length in a concentric fashion in such a way that the respective axes of the plurality of small diameter combustion assisting gas-ejecting ports focus at one point; ejecting a glass raw material from the glass raw material gas-ejecting port; ejecting a flammable gas from the flammable gas-ejecting port arranged outside the glass raw material gas-ejecting port; ejecting a combustion assisting gas from the plurality of small diameter combustion assisting gas-ejecting ports; hydrolyzing a glass raw material gas ejected from the glass raw material gas-ejecting port to generate glass particles; depositing the glass particles on a rotating starting material in the radial direction; increasing feed rates of the respective gases from the start of the deposition to the end of the deposition; making L1 greater than L2 (L1>L2) during the early stage of the deposition where a focal length of the plurality of small diameter combustion assisting gas-ejecting ports is defined by L1 and a distance from the tip of the plurality of small diameter combustion assisting gas-ejecting ports to a deposition plane of the glass particles on the starting material is defined by L2; and making L2 increased during the course of the deposition so that L2 is greater than L1 (L1