| 摘要 |
After the start of the control operation of a drawing apparatus, the operation control of a line speed being the drawing-in speed of an optical fiber is performed by a line speed control unit (19), and an optical-fiber feed speed control is performed by a preform feed speed control unit (22), in order that an optical fiber outside diameter measured by an optical-fiber outside diameter measurement unit (8) may become a target outside diameter. By way of example, in a case where the distal end of an optical fiber preform is not in a shape steadily melted in a heating furnace, the preform speed control unit (22) controls the feed speed of the optical fiber preform in the three stages of an optical-fiber-preform initial feed speed control, an acceleration-associated preform feed speed control and a line speed-associated preform feed speed control. In a case where the distal end of the optical fiber preform is in the steadily melted shape, the unit (22) controls the preform feed speed in two stages in which the acceleration-associated preform feed speed control is omitted from the three stages. In optical fiber drawing, troubles such as the breaking of the optical fiber can be suppressed even during the acceleration of the line speed.
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