| 摘要 |
A fiber optic coupler and method for forming such coupler is shown in which the substance of the fibers (12, 14) is preselected to have a heat fusing temperature in a range achievable by exterior heating of a shrink sleeve (18), and the fibers (12, 14) are heat fused-together along a limited length region within the shrunken sleeve (18) as a result of heat and inter-fiber pressure applied to the fibers (12, 14) by exterior heating of the shrink sleeve (18). In preferred embodiments, a filler rod (50) is disposed alongside the optical fibers (12, 14) and pressed thereagainst by the shrink sleeve (18), the exterior of the rod (50) preferably of fluorocarbon plastic, having an index of refraction lower than the index of refraction of the fibers (12, 14) in the fused region. The interior of the filler rod (50) preferably comprises an elongated heat transfer element (52, 56) having a heat transfer coefficient greatly exceeding the heat transfer coefficient of the fibers (12, 14). Where few fibers are involved, the fibers are twisted about themselves and the filler or heat transfer element is substantially straight. For larger numbers of fibers, such as more than four, the fibers are loosely introduced in substantially parallel condition to fill the sleeve and are fused together by heating of the sleeve. A plastic coupler is also featured in which the cladding layer (32) is completely absent in a fused region, and the cores (34) in that region are deformed and fused together in a core-mode coupling relationship as the result of application of inter-fiber pressure under fusing conditions, preferably heat fusing conditions. Preferably the clad layer (32) is removed by solvent and care is taken to ensure that the exposed portion of core (34) has effective cladding, e.g. by action of a sleeve (18), a filler rod (50) and air spaces. Other important features relating to ease of manufacture and improvements in performance of optic fiber couplers are disclosed. |
