Large Signal Analysis of the Mach-Zehnder Interferometer with One Arm Loaded with a Second-Order Allpass Double-Microring Resonator

A mathematical model for the transfer function of the Mach-Zehnder interferometer with one arm loaded with a second-order allpass double-microring resonator (2R-MZI) is presented. The model, basically a sine-series function, can easily yield closed-form expressions for the amplitudes of the harmonic and intermodulation components of the output when the input is formed of large-amplitude multisinusoidal RF voltage. The special case of two-tone equal-amplitude RF input voltage is considered in detail. The results show that the third-order intermodulation component is always higher than the third-harmonic component. The results also show the extensive improvement in the linearity of the Mach-Zehnder interferometer with one arm loaded with a second-order allpass microring resonator. Compared with the standard Mach-Zehnder interferometer, the results show that a sharp reduction of 80 dB in the third-order intermodulation can be achieved.