Patent ID: 8417077

Claim:
An optical branching device, comprising: a multicore optical fiber comprising a first core extending along a predetermined axis, one or more second cores, and a cladding surrounding the first and second cores; the multicore optical fiber having a first end face, a second end face opposing the first end face, an entrance port A, positioned on the first end face, for guiding light from the outside to the first core, and a plurality of exit ports B, positioned on the second end face, for taking out light propagated through the first and second cores; and a fan-out part having a third end face opposing the second end face of the multicore optical fiber, a fourth end face opposing the third end face, a plurality of entrance ports C positioned on the third end face and arranged so as to optically couple with the plurality of exit ports B, and a plurality of exit ports D arranged on the fourth end face so as to correspond to the plurality of entrance ports C, respectively, and have a center-to-center distance longer than that of the plurality of entrance ports C, wherein the number of the exit ports B is greater than that of the entrance port A but is equal to or less than the total number of the first and second cores; and wherein at least a part of the light incident on the first core through the entrance port A is branched to the second core by core-to-core crosstalk.