The basic embodiment of the present invention comprises an optical fiber having cores and a claddings, and core-extensions, wherein the individual core-extensions are built onto the core end facets in a shape of the diverging horn-like structure, with the sectional area increasing gradually as the individual...http://www.google.com/patents/US5287424?utm_source=gb-gplus-sharePatent US5287424 - Optical fiber coupler with overlapping core-extensions, and manufacturing methods of the same
