PRODUCTION OF HALIDE GLASS FIBER PREFORM

摘要

PURPOSE: To facilitate the production of a halide glass fiber preform having a high core-to-clad ratio while preventing the intrusion of air bubbles at the boundary between a core and a clad and preventing the occurrence of crystallization by making the sectional shape of the core uniform. CONSTITUTION: A core rod 1 having a uniform square section is independently formed of halide glass for the core in a longitudinal direction in a core forming stage Pl. Separately, four divided rods 2, 2,... each having a rectangular shape are formed of the halide glass for the clad in a divided rod forming stage P2. The respective divided rods are arranged circumferentially in such a manner that the core rod exists at the center and the core rod and the respective divided rods as well as the adjacent divided rods are held in the state of pressing these rods to each other over the entire surface continuously in the longitudinal direction to form combined fiber preforms in a combining stage P3. The combined fiber preforms are integrated by heating in a reduced pressure state and in an inert gaseous atomophere in an integrating state P4, by which the integrated fiber preform 4 consisting of the core 4a and the clad 4b is obtd.