Patent ID: RE44262

Claim:
An optical coupler which comprises: (a) a bundle of a plurality of multimode fibers having a few-mode fiber in the center, said few-mode fiber being a signal fiber through which an optical signal is transmitted; (b) a large area core double clad fiber (LACDCF) having an inner cladding and an outer cladding with a lower refractive index, and having an end portion terminating with an input end the inner cladding of which has a predetermined circumference, into said input end of the LACDCF the optical signal is to be transmitted from said few-mode fiber; (c) said bundle having a fused end portion with an output end having a periphery that fits within the circumference of the inner cladding of the input end of the LACDCF; and (d) said output end of the bundle being aligned and spliced with the input end of the LACDCF in such a way as to preserve fundamental mode transmission from the few-mode fiber to the LACDCF.