METHOD AND DEVICE FOR PRODUCING COVERED OPTICAL FIBER AND COVERED OPTICAL FIBER

摘要

A method of producing a covered optical fiber (21) comprising the steps of drawing a glass fiber (13) after heating and softening one end of an optical fiber base material (11), applying coating (16, 19) onto the glass fiber (13), letting the covered optical fiber (21) pass through a periodically swinging guide roller (23) to twist the covered optical fiber (21), and thereby imparting the glass fiber (13) inside the covered optical fiber (21) twisting around the axis, wherein the covered optical fiber (21) passed through the guide roller (23) is allowed to pass through a free section (26 through 27) permitting a free turning on the axis to thereby offset longitudinally an elastic torsion accumulated when the covered optical fiber (21) is alternately reversed in its longitudinal twisting directions, a length (L) (m) of the free section being at least Lo (m) defined by Lo (m)= (maximum production line speed (m/min))/(number of back-and-forth swings per unit time of swinging guide roller (number/min)).