Patent ID: 8515220

Claim:
An optical fiber coupler configured to receive signal beams from a plurality of input optical fibers to produce a non-circularly shaped output optical beam, the coupler comprising: an adiabatically tapered optical device having one or more cores with a first core diameter, one or more claddings, and a first mode field diameter at an input end of the tapered optical device, and a second core diameter and a second mode field diameter at an output end of the tapered optical device, the tapered optical device has a core taper ratio equal to the ratio between the second core diameter and the first core diameter, and a mode taper ratio equal to the ratio between the second mode field diameter and the first mode field diameter, the tapered optical device is configured to be directly attached to the plurality of input optical fibers at the input end and to produce the non-circularly shaped output beam at the output end, wherein the mode taper ratio is greater than the core taper ratio, wherein a spacing between adjacent cores at the output end is less than a spacing between adjacent cores at the input end by approximately the core taper ratio, thereby increasing brightness of a combined output optical signal relative to the combined brightness of the plurality of input optical fibers by a factor approximately equal to the ratio of the mode taper ratio to the core taper ratio.