| 摘要 |
PROBLEM TO BE SOLVED: To provide a production method for an optical fiber preform which can stably produce an optical fiber with a low loss and excellent resistance to hydrogen without requiring expensive deuterium; and an optical fiber. SOLUTION: The production method for the optical fiber preform comprises depositing glass fine particles by a VAD method to form core soot having a core and a part of a clad, dehydrating/transparently vitrifying the core soot to yield a core rod, and forming thereon a clad. In forming a clad by heating the side of a core formed by the deposition of glass fine particles, a raw material gas containing fluorine is supplied to at least one burner. The proportion of fluorine in the raw material gas is set at such a level that the refractive index profile of the optical fiber yielded by drawing substantially presents a depressed clad shape. The resultant core soot is transparently vitrified by causing it to continuously pass through a vitrification heating zone having a heater with a height of H [mm], at a speed of V [mm/min] so that the heater passing time HV≤50 [min], thus giving the core rod. COPYRIGHT: (C)2005,JPO&NCIPI
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