| 摘要 |
Fiber optic splitters having a central fiber (18, 21) and a selectable numbe r of surrounding fibers (10, 20) with mutual con- tact among the surrounding fibers and central fiber, formed preferably of identical diameter starting fibers. According to a for- mula, between three and five surrounding fibers, the central fiber (18, 21) has a reduced diameter, while for seven or more sur- rounding fibers, the diameters of the surrounding fibers are reduced. Splitters with one input and four, eight, twelve, or sixteen equal outputs, having a flattened wavelength response are provided. Means ar e provided to reduce detrimental phase mismatch at the desired coupling ratio as by substantially matching the propagation constants of the central and surrounding fibers in the fin- ished coupler. Provisions for sufficiently matching the propagation constant s include making the fused splitter region short; start- ing with fibers having differing propagation constants selected so the difference is diminished during fusing; fusing the fibers to- gether to the extent that there are substantially no interstitial voids in t he coallesced fiber mass; and surrounding the surrounding fibers (10, 20) with a transparent substance having the effect of cladding. For the latter purpose, a tube (11) or transparent optical rods assembled about the surrounding optical fibers are fused therewith, or the transparent substance is a moldable substance ap- plied after the fused region of the coupler has been formed.
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