METHOD AND DEVICE FOR PRODUCING COVERED OPTICAL FIBER

摘要

In a fabrication method of coated optical fiber 21, the coated optical fiber 21 is fabricated by heating to soften an end of an optical fiber preform 11 to draw a glass fiber 13 out therefrom, laying coatings 16, 19 on the glass fiber 13 to make the coated optical fiber 21, and guiding the coated optical fiber 21 via a swing guide roller 23 periodically swinging, to twist the coated optical fiber 21, thereby imparting twists about the axis to the glass fiber 13 inside the coated optical fiber 21. The fabrication method comprises a step of passing the coated optical fiber 21 having passed the swing guide roller 23, through a free zone (between 26 and 27) in which the coated optical fiber 21 is allowed to freely rotate about the axis, and thereby longitudinally canceling out elastic torsion stored in the coated optical fiber 21 because of longitudinally alternate inversion of twist directions thereof, wherein a zone length L (m) of the free zone is not less than Lo (m) defined as follows: Lo (m) = Äa maximum drawing speed of the coated optical fiber (m/min)Ü/Äthe number of clockwise and counterclockwise swing motions per unit time of the swing guide roller (motions/min)Ü.