A 80 Gb/s PAM4 CMOS Transmitter Integrated with Two-Segment Silicon Microring Modulator

This paper presents a quarter-rate CMOS transmitter (TX) integrated with a two-segment silicon-based microring modulator (MRM). The AC-coupled pulsed-cascode high-swing voltage-mode MSB/LSB drivers achieve a 3.42 Vppd swing and offer independent level-tuning, edge-rate control, and asymmetric pre-emphasis on rising and falling edges. Implemented in a 28 nm CMOS process and co-packaged with the MRM via wirebonding, the proposed TX operates at 80 Gb/s PAM4 with a power efficiency of $3.66 \mathrm{pJ} / \mathrm{bit}$.