No abstract

A nested Mach-Zehnder interferometer (MZI) configuration whose phase shifters are placed in parallel is suitable for silicon-silica hybrid structure to realize a high-speed optical switch. Even when the signal wavelength deviates from an optimal wavelength, the crosstalk of the nested MZI optical switch can be suppressed by employing phase generating couplers (PGCs) in place of directional couplers. We calculate the characteristics of a 4-stage nested MZI switch with PGCs, and show that crosstalk is lower than −40 dB over a wavelength range of as wide as 200 nm from 1450 to 1650 nm in six output ports. We also examine the scalability of the multi-stage nested MZI switch, and deduce the required number of switch stages for given output port counts with low crosstalk.