Silicon Photonic Microring-Based 4 × 112 Gb/s WDM Transmitter With Photocurrent-Based Thermal Control in 28-nm CMOS

This work presents a hybrid-integrated 4- $\lambda $ micro-ring modulator-based wavelength-division multiplexed (WDM) optical transmitter (OTX) in the O-band, suitable for co-packaged optics. It supports up to 112 Gb/s per wavelength using high-bandwidth micro-ring modulators (MRMs) together with nonlinear equalization in the driver electronics. A thermal control scheme using MRM photocurrent to sense process and temperature variations is implemented, enabling <0.05 dB TDECQ penalty over 10 °C. This compact photocurrent-based control method significantly reduces the hardware and packaging overhead required for ring-based WDM transceivers. Measurements from a 4- $\lambda $ OTX with 28-nm CMOS electronic IC (EIC) and custom silicon photonic IC (PIC) show the OTX supports 112 Gb/s with <0.7 dB TDECQ across all four channels while dissipating 5.8 pJ/bit in the electronics.