Fiber optic coupler

A method of forming a fiber optic coupler by means of shrinking a sleeve of heat shrink plastic about a plurality of optical fibers, each fiber having an optically transmissive core surrounded, along at least most of its length, by an optical cladding layer, characterized in that the substance of said fibers is preselected to have a heat fusing temperature in a range achievable by exterior heating of said shrink sleeve, said method including the steps of assembling said fibers in a coextensive relationship within said sleeve, and applying external heat to said sleeve sufficient to shrink said sleeve to apply interfiber pressure between said fibers while, through the substance of said sleeve, heating said fibers to said fusing temperature sufficient to cause said fibers to heat fuse together in a coupling relationship over a limited length region and thereafter allowing said assembly to cool.

A fused fiber optic coupler comprising a plurality of fibers each fiber having an optically transmissive core surrounded, along at least most of its length, by an optical cladding layer, the fibers being fused together along a region of their length to provide optical coupling between the fibers, characterized in that the cores and the cladding layers of said optical fibers are comprised of plastic, the cladding layer being completely absent in said fused region, and the cores in said region being deformed in cross-sectional area in a core-mode coupling relationship as the result of simultaneous application of radial inter-fiber pressure and fusing conditions.

A fused fiber optic coupler comprising more than about four fiber optic fibers, each fiber having an optically transmissive core surrounded, along at least most of its length, by an optical cladding layer, the fibers, which extend along each other in a generally straight, untwisted relationship being fused together along a region of their length to provide optical coupling between the fibers, characterized in that the cores and the cladding layers of said optical fibers are comprised of plastic, the cladding layer being completely absent in said fused region, and the cores in said region being deformed and fused together in a core-mode coupling relationship to each other as the result of application of inter-fiber pressure throughout said region to be fused under fusing conditions.

A method of forming a fused fiber optic coupler by fusing a plurality of fibers together along a region of their length to provide optical coupling between the fibers, characterized by the steps of providing optical fibers having cores and cladding layers comprised of plastic, completely removing the plastic cladding layers of each fiber in a region to be fused, placing said regions of said fibers alongside one another, and, under fusing conditions, simultaneously applying radial inter-fiber pressure to deform said cores in cross-sectional shape and fuse said cores together in a core-mode coupling relationship without change in length or cross-sectional area.

A fiber optic coupler comprising at least two plastic optical fibers joined in intimate contact by fusing along a limited length segment,

• each said fiber, in said limited length segment, comprising a core and, disposed about said core, significantly less cladding material than in a region of each said fiber outside said limited length segment, and
• disposed about said fibers along at least a portion of said limited length segment, a sleeve of shrink material treated to encircle said fibers in a manner to urge said fibers into intimate fused contact.