Method for making optical fiber couplers

Abstract

An apparatus and method are described for making an optical fiber coupler. A pair of optical fibers are supported in predetermined orientation by positioning means. The latter are spaced apart along a common axis. The optical fibers are positioned within tube means of a selected size intermediate the positioning means. In use, the tube means functions as a furnace to distribute heat uniformly to at least a portion of the fibers to fuse the same together. One of the positioning means preferable is rotatable, to enable twisting of the fibers. It is also preferable that at least one fiber has a tensile force applied to it. More preferably, the tensile force is sufficient to cause necking of the heated fiber, thereby forming a biconical section therein. Rotation of one positioning means through about one half revolution normally causes twisting of the biconical section and fusion thereof to the other fiber. Typically, both fibers are subject to a pulling force to create biconical sections. In an automated system the fibers are of indeterminate length, fed through a furnace and simultaneously given a twist to couple and fuse sections of fiber together. The fibers may already have biconical sections therein; or such sections can be formed by applying a sufficient tensile pull to each heated fiber to cause necking of the same. The couplers may be made from two or more optical fibers. Each fiber may be of the same, or different, diameters.