Formation of fiber optical coupler

PURPOSE: To efficiently form a fiber optical coupler by compressing a glass tube onto optical fibers and arranging plural pieces of output fibers at equal intervals around one piece of input fiber. CONSTITUTION: The glass tube 10 formed with, for example, four pieces of projecting lines 24 which are arranged at equal intervals on the inside wall surface of an axial hole 11, extend in a longitudinal direction and project inward is prepd. Plural pieces of the glass optical fibers 20 are arranged into the axial hole 11 in the form that the respective fibers 20 exist between a pair of the adjacent projecting lines 24. The axial hole 11 has a section of a regular polygonal shape. Tapered apertures 12, 13 pass flames into the tube so as to generate a temp. gradient in an axial line direction, thereby softening the materials to collapse. The intermediate region of the tube 10 is at least partly stretched, by which the optical coupler is formed. COPYRIGHT: (C)1992,JPO