| CPC C03B 37/01869 (2013.01) [C03B 37/01205 (2013.01); C03B 37/025 (2013.01); C03B 37/027 (2013.01); C03C 25/68 (2013.01); C03B 2201/50 (2013.01)] | 9 Claims |
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1. A method for manufacturing an optical fiber preform including a core part and a cladding part, comprising:
adding an alkali metal to an inner surface of a silica-based glass pipe;
etching the inner surface of the silica-based glass pipe to which the alkali metal is added;
making a glass rod by collapsing the silica-based glass pipe after the etching; and
making an optical fiber preform using the glass rod,
wherein the silica-based glass pipe is heated in the adding such that a surface temperature of the silica-based glass pipe falls within a temperature range of 1500° C. or higher to lower than 2000° C. while a space in which the silica-based glass pipe is held is kept at a positive pressure above atmospheric pressure of greater than 0 Pa and 20 Pa or less,
wherein the silica-based glass pipe is heated by reciprocatively traversing a heat source a plurality of times, the heat source being an oxyhydrogen burner,
wherein in the adding, a heating time per traverse of the reciprocatively traversing with which a surface temperature of a predetermined area of the silica-based glass pipe falls within the temperature range of 1500° C. or higher to lower than 2000° C. is 0.5 minute or longer and shorter than 40 minutes,
wherein the heating time is a time during which a certain point in the silica-based glass pipe is heated to 1500° C. or higher, and
wherein a traverse speed of the oxyhydrogen burner is 10 mm/min or greater and 165 mm/min or less.
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