METHOD FOR COUPLING OPTICAL FIBER WITH LENS

PURPOSE:To set the distance between a lens and optical fiber and to align their optical axes without making any adjustment works, by arranging >=3 balls which are respectively in contact with three points on the end face of a cylindrical ferrule fixing the optical fiber with its central part, inner surface of a precision sleeve having cylindrical holes for holding the ferrule in an arranged condition, and spherical surface section of the lens. CONSTITUTION:A lens 13 is fixed by screwing its lens holder 14 in a precision sleeve 12 after >=3 balls 15 which are respectively in contact with three points on the end face of a ferrule 11 fixing an optical fiber 10, the inner surface of the precision sleeve 12 holding the ferrule 11, and the surface of the spherical lens 13 are arranged. Therefore, the center of the lens 13 is aligned to the center line of the hole of the precision sleeve 12 and, accordingly, to the optical axis of the optical fiber 10 fixed to the center of the ferrule 11. Moreover, the distance between the lens 13 and end face of the optical fiber 10 is determined by the diameter of the balls 15. The distance (l) between the lens 13 and end face of the optical fiber 10 (end face of the ferrule 11) is determined from the focal length of the lens 13 and the diameter 2r of the balls can be calculated from the formula I .