An optical coupler comprising: a bundle comprising a plurality of multimode fibers (16, 18) and a signal fiber, said bundle comprising a fused end portion with an output end having a periphery, said signal fiber being substantially located at the center of said fused end portion, said signal fiber being a fiber having a core through which an optical signal is to be transmitted; and a double cladding fiber, DCF, having a core through which said signal is to be transmitted, an inner cladding having a first refractive index, and an outer cladding having a second refractive index, said DCF having an end portion terminated by an input end having a predetermined circumference; characterized in that: said signal fiber of said bundle is a few-mode fiber; said DCF is a large area core DCF, LACDCF,; and said output end of said bundle and said input end of said LACDCF are aligned and fusion-spliced such that said periphery of said output end of said bundle fits within said predetermined circumference of said inner cladding at said input end of said LACDCF, and such that said core of said few-mode fiber is precisely modally aligned and matched with said core of said LACDCF such as to preserve fundamental mode transmission from said core of said few-mode fiber to said core of said LACDCF, and wherein the few-mode fiber at the output end is a fiber with a core expanded from a single mode fiber. a bundle comprising a plurality of multimode fibers (16, 18) and a signal fiber, said bundle comprising a fused end portion with an output end having a periphery, said signal fiber being substantially located at the center of said fused end portion, said signal fiber being a fiber having a core through which an optical signal is to be transmitted; and a double cladding fiber, DCF, having a core through which said signal is to be transmitted, an inner cladding having a first refractive index, and an outer cladding having a second refractive index, said DCF having an end portion terminated by an input end having a predetermined circumference; characterized in that: said signal fiber of said bundle is a few-mode fiber; said DCF is a large area core DCF, LACDCF,; and said output end of said bundle and said input end of said LACDCF are aligned and fusion-spliced such that said periphery of said output end of said bundle fits within said predetermined circumference of said inner cladding at said input end of said LACDCF, and such that said core of said few-mode fiber is precisely modally aligned and matched with said core of said LACDCF such as to preserve fundamental mode transmission from said core of said few-mode fiber to said core of said LACDCF, and wherein the few-mode fiber at the output end is a fiber with a core expanded from a single mode fiber. said signal fiber of said bundle is a few-mode fiber; said DCF is a large area core DCF, LACDCF,; and said output end of said bundle and said input end of said LACDCF are aligned and fusion-spliced such that said periphery of said output end of said bundle fits within said predetermined circumference of said inner cladding at said input end of said LACDCF, and such that said core of said few-mode fiber is precisely modally aligned and matched with said core of said LACDCF such as to preserve fundamental mode transmission from said core of said few-mode fiber to said core of said LACDCF, and wherein the few-mode fiber at the output end is a fiber with a core expanded from a single mode fiber.