| 摘要 |
An achromatic fiber optic coupler of the type wherein a plurality of single-mode optical fibers, each having a core and a cladding, are fused together along a portion of the lengths thereof to form a coupling region. The propagation constants of the fibers are preferably equal; however if the fiber claddings have different refractive indices, the lowest cladding refractive index is n2. A matrix glass body of refractive index n3 surrounds the coupling region, n3 being lower than n2 by such an amount that the value of .DELTA.2-3 is less than 0.125%, wherein .DELTA.2-3 equals (n22-n32)/2n22.
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