Star couplers using fused biconically tapered multimode fibres

We report the fabrication and testing of 4-, 7-and 19-fibre fused biconical taper transmissive star couplers for use with single multimode fibres. Overall insertion losses on six couplers range from -1.3 dB to -2.6 dB. Losses are nearly independent of N, the number of fibres, but dispersion of the powers in the output fibres increases significantly with N.