An 80 Gb/s Silicon Photonic Modulator Based on the Principle of Overlapped Resonances

We report a silicon photonic modulator based on a Mach-Zehnder interferometer (MZI) loaded with a microring modulator (MRM) on one arm and a microring resonator (MRR) on the other arm. The device is operated with the resonances of the MRM and the MRR overlapped to improve the extinction ratios and the optical modulation amplitudes. The operating principle is studied in detail using an analytical model. The measured 3-dB electro-optic bandwidth of the device is 27.4 GHz under 0-V reverse bias voltage. In the back-to-back configuration, the modulator has error-free performance up to 38 Gb/s using on-off keying (OOK) modulation without digital signal processing (DSP). At 56 Gb/s, using four-level pulse amplitude modulation (PAM-4) with DSP, the measured bit error rate (BER) is below 1 × 10
^-6
. We further present successful 56 Gb/s OOK transmission and 80 Gb/s PAM-4 transmission over 2 km of standard single mode fiber, with measured BERs below the hard-decision forward error correction threshold of 3.8 × 10
^-3
.