Low-crosstalk, short-length mismatched optical coupler designed by new weighting function

A newly self-developed Broadband weighting function is presented to show the excellent results comparing with the Blackman and Hamming weighting function in applying to the waveguide structure of mismatched optical couplers for the demand of short-length, C+L-band, and low crosstalk. It is found that the coupler with the Broadband weighting function can reach the bandwidths between 1.360 to 1.700 µm with a coupling length of 2.5 mm and crosstalk of −35 dB. Obviously, the Broadband WF is suited in weighting the waveguide structure of a mismatched optical coupler to obtain a short coupling length, low crosstalk, and broad bandwidth.