Abstract: The end face of an optical fiber assembly consisting of an optical fiber s and a ferrule f is polished to form a conical surface with oblique faces Fp1 and Fp2 such that, central axis Ap of the conical surface makes an inclination of 8.degree. with respect to the optical axis L of the optical fiber s, top Ft of the conical surface coincides with the optical axis L of the optical fiber s, and has a taper angle of 2.degree.. Thereafter, the optical fiber assembly is further polished to form an oblique convex spherical surface at the end face such that, the central axis of the oblique convex spherical surface makes an inclination of 8.degree. with respect to the optical axis L of the optical fiber s. Due to this, insertion loss and light reflected back to the source is stabilized and minimized.

Abstract: End face of a ferrule 100 is polished to form a conical surface 3 such that, central axis Ap of said conical surface 3 makes an inclination of 8.degree. with respect to central axis L of optical fiber insertion hole 4, top 3t of said conical surface 3 coincides with said central axis L and has a taper angle of 2.degree.. Because of this, while polishing an end of a optical fiber inserted and fixed inside said optical fiber insertion hole 4, a well balanced oblique spherical surface can be formed and the non-coincidence of the center of said oblique convex surface with the point where said oblique convex surface intersect with the optical axis of said optical fiber can be prevented.