Abstract: There is provided a core pin for injection molding of a ferrule accompanied by a small amount of wear by forming a core pin constituted by a circular cylinder portion having a first diameter at a portion thereof for forming one end face of the ferrule and having a first angle of inclination by which a diameter thereof is enlarged toward other end thereof, a circular cone portion having a second diameter larger than the first diameter at a portion thereof for forming other end of the ferrule and having a second angle of inclination an angle of which is larger than the first angle of inclination by which a diameter thereof is reduced toward the one end face and a curved face in contact with the circular cylinder portion and the circular cone portion and having a section in a circular arc shape.

Abstract: A split sleeve material is generally in a cylindrical form to have penetrating grooves extending in an axial direction and, at respective end portions, annular end portions where the penetrating groove is not formed over an entire periphery thereof. A split sleeve is formed by cutting the annular end portions.

Abstract: A sleeve for connecting ferrules supporting optical fibers has a tubular body having a first end surface, a second end surface opposite the first end surface, an inner peripheral surface, and an outer peripheral surface. Convex projections are disposed on the inner peripheral surface of the tubular body and extend continuously from the first end surface to the second end surface of the tubular body.