| 摘要 |
PROBLEM TO BE SOLVED: To suppress bending of a preform rod when a preform rod is produced by stretching an optical fiber preform ingot, by using a specified rod center position detecting means attached to the lower part of a heater for the preform to measure the bending state or the bending direction of the rod and then controlling the position of a rod receiving device according to the measured value. SOLUTION: A preform ingot 1 is set in a stretching furnace 6 equipped with a heater 5, sealing material 11, fixing part 3 for the preform, and stretching is started after the ingot is heated. When the preform rod 2 passes through a laser measuring device comprising two pairs of light-projecting part 41 and light-receiving part 42 arranged in such a manner that beams cross perpendicular to each other on three positions A, B, C, the information about the position on the coordinate of the center on each point A, B, C is sent from each light- receiving part to a controller 10. From the measured values, the bending amt. and bending direction of the rod are calculated, and a X-Y table 8 is controlled to move by a moving amt. calculating controlling unit (included in the controller 10) according to the calculated values so as to make the center axis of the rod vertical and to continue stretching. |
