To improve the leading characteristic of an optical fiber unit by forming the sectional shape of a sheath to a shape which comes into contact with at least two points with one plane parallel with the plane on which optical fibers are lined up.
The coated optical fiber 2 is constituted by lining plural pieces of the optical fibers 1 in parallel on the same plane X and forming an integral coating layer on their circumference, thereby integrating these fibers. The sheath 3 is formed by extrusion coating around the coated optical fiber 2. The sectional shape of the sheath 3 is formed to the shape that the outer peripheral surface of the sheath 3 and the one plane parallel with the plane X come into contact with each other at least at two points. The sectional shape of the sheath 3 is formed to the shape obtd. by cutting, for example, the circular upper and lower parts at the plane 3a parallel with the plane X. Foamed polyethylene is usable as the material of the sheath 3.
MOGI AKIO
MIYAMOTO SUEHIRO
ARAKI SHINJI
