要約

Formation of the biconic region is a key link in the chain of technological operations when fabricating fused fiber-optical multiport distributor-combiners constructed from a bundle of fiberguides. It is at this stage that the basic parameters of fabricated distributor-combiners are set, namely, the intrinsic loss and the distribution of input radiation power between the output channels. A higher level of intrinsic loss (compared with loss in fiber-optical distributor-combiners of other types) as well as an essentially nonuniform optical power distribution between the output channels of a fused distributor-combiner are caused by specific features of the propagation of radiation inside the biconic region. The biconic region of a high-quality fiber-optical distributor-combiner must provide for:

• effective transmission of radiation from the input fiberguide cores into the narrowing part of the biconic region and capture of radiation by the fiberguide cores of the output ports in the widening part of the biconic region;
• multiple reflection from the "biconic region-air" interfaces with radiation confinement in the biconic region.

It follows from general considerations that the geometric parameters of the biconic region must satisfy conflicting demands. On the one hand, the generatrices of the biconic region should be markedly inclined to its axis in order to provide for an efficient optical output from the lightguide cores where the section narrows and the subsequent reliable capture of optical energy by the cores where the section widens. On the other hand, the inclination must not be too large, so that the angle of the rays leaving the input cores remain below critical for multiple reflections from "biconic region-air" interface.