Tapered mode multiplexers based on standard single-mode fibre

We report mode multiplexers with single-mode inputs directly compatible with standard telecoms fibres. They are made by fusing and tapering three such fibres in a fluorine-doped silica capillary. The fused fibres act as the core of a multimode fibre, in which three individual modes could be separately excited. The loss is 0.6-0.7 dB.