To provide an optical fiber, in which the work of tearing a coat can be easily performed without making manufacture troublesome.
When a long diameter direction on the cross sectional surface of the coat 3 is defined as an X axis direction and a short diameter direction is defined as a Y axis direction, a coated optical fiber 1 for which two or more cores are arranged in the X axis direction and two or more cores are arranged in the Y axis direction is used, and tensile strength body 5 and 5 are arranged on both sides in the X axis direction of the coated optical fiber 1 on the cross sectional surface of the coat 3. On the coat 3, two pairs of notches A, A' and B, B' are formed facing each other at both side face parts in the Y axis direction, and two straight lines connecting the notches A, B and A', B' facing each other on the cross sectional surface of the coat 3 are roughly parallel with the Y axis to pass through both end parts in the X axis direction of the coated optical fiber 1. Tear forces Fna and Fnb, when simultaneously tearing the coat 3 at the respective notches A, A' and B, B' on one side, are equal to or smaller than the rupture strength Fja and Fjb of a coat piece.
OKADA NAOKI
KUNO JUN
Iwa Saki Kokuni
Shunichi Takahashi