A 80 Gb/s PAM4 All-Silicon Ring-Based Optical Transmitter With CMOS IC

Microring resonator modulators (MRM) alongwith four-level pulse amplitude modulation (PAM4) can efficiently scale to higher data-rates on a single channel when combined with CMOS chips. In this work, we present an all-silicon ring-based optical transmitter (TX) which consists of a two-segment MRM heterogeneously integrated over wirebonds with a CMOS IC implemented in 28 nm CMOS process. The MRM device characteristics are modeled in Verilog-A which enables efficient co-simulation. The CMOS TX consists of individual PAM2 AC-coupled pulsed-cascode high-swing voltage-mode drivers for MSB/LSB segments. The drivers achieve a 3.42 Vppd swing and offer independent level-tuning, edge-rate control, and asymmetric post-cursor pre-emphasis on rising and falling edges. The proposed TX operates at 80 Gb/s PAM4 with a power efficiency of 3.66 pJ/bit.