| 摘要 |
PROBLEM TO BE SOLVED: To provide a method for producing an optical fiber preform, using a simple facility and production method, and capable of reducing outer diameter differences in its longitudinal direction. SOLUTION: This method for producing an optical fiber preform by heat- treating a porous glass material 1 formed by a gas phase synthesizing method, has a first heat-treating process of passing the material 1 through a heating zone while moving the material 1 in an arrow mark B direction for false- shrinking the material 1, and a second heat-treating process of moving the treated material 1 by the first heat-treating process in the arrow mark B direction, passing the material 1 through a heating zone being a higher temperature than that of the first heat-treating process to form a transparentized glass material, and the moving speed of the material 1 is changed in at least one of the processes in the first and second heat-treating processes.
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