Optical coupler, a method of its fabrication and use

An optical coupler for coupling light from at least two input fibers into one output fiber and a method of fabricating and use of an optical coupler. The coupler comprises a) an input section comprising an output end face at one end of the bundling-length of input fibers; and b) an output section comprising an output fiber comprising a confining region for confining light propagated in the input fibers and a surrounding cladding region and having an input end face; wherein the output end face of said input section is optically coupled to the input end face of the output section and at least the confining region of the output fiber is tapered down from a first cross sectional area at the input end face to a second, smaller cross sectional area over a tapering-length of the output fiber.