Demonstration of Flat-Passband Multi/Demultiplexer Using Multi-Input Arrayed Waveguide Grating Combined With Cascaded Mach–Zehnder Interferometers

We demonstrate multi/demultiplexers with a very flat passband and small excess loss using a multi-input arrayed waveguide grating combined with a cascaded Mach-Zehnder interferometer structure. We also analyze the impact of coupling between input waveguides just before the input slab on chromatic dispersion and investigate a waveguide structure for reducing the chromatic dispersion. We fabricated flat-passband multi/ demultiplexers with 100-GHz channel spacing using 2.5%-Delta silica waveguides and experimentally investigated the dependence of their optical characteristics on design parameters to demonstrate the effectiveness of the proposed theoretical model. We obtained a very flat passband response having a 1-dB bandwidth of 0.645-0.658 nm and 20-dB bandwidth of 0.944-0.960 nm with a loss penalty due to the passband-flattening of 0.9-1.0 dB and chromatic dispersion of -22.1-17.5 ps/nm over 0.5 nm in the passband. The measured passband shape and chromatic dispersion generally agreed with the simulation results.