FABRICATION METHOD OF OPTICAL FIBER PREFORM AND OPTICAL FIBER CONTAINING FEW HYDROXYL GROUPS

摘要

A method for fabricating an optical fiber preform and an optical fiber having few hydroxyl groups in a core layer using MCVD is disclosed. This method includes forming a clad layer on an inner wall of a substrate tube, and forming a core layer on the clad layer. The core layer forming process includes a soot deposition step for generating and depositing soot on the clad layer by heating the substrate tube with supplying soot-forming gas into the substrate tube in which the clad layer is already formed, a dehydration step for removing hydroxyl groups and moisture from the deposited soot and the substrate tube by supplying dehydration gas into the substrate tube, and a sintering step for sintering the soot by heating the substrate tube at a high temperature. During the dehydration step and/or the sintering step, an evaporated heavy water (D20) is supplied.