A 112 Gb/s PAM4 Silicon Photonics Transmitter With Microring Modulator and CMOS Driver

Microring modulators (MRMs) with CMOS electronics enable compact low power transmitter solutions for 400G Ethernet and future on-package optical transceivers. In this paper, we present a 112 Gb/s PAM4 transmitter using silicon photonic MRM, on-chip laser and co-packaged 28 nm CMOS driver. We describe the impact of static and dynamic MRM nonlinearity on PAM4 signaling and present a dual path nonlinear pre-distortion technique to compensate both effects. PAM4 measurement results of our transmitter at 112 Gb/s show that TDECQ <; 0.7 dB is achieved from 30 °C to 60 °C while dissipating 6 pJ/bit. We also present link level measurements at 112 Gb/s PAM4 obtained by coupling this transmitter with our previously published CMOS TIA-based receiver, to demonstrate the feasibility of low cost optical transceivers through CMOS integration of optical interface circuits.

I. Introduction

The rapid growth of internet traffic and data-centric computing is driving the need for high bandwidth, low cost interconnect solutions for the data center. 100+ Gb/s links capable of spanning distances from meters to kilometers are required to meet this demand, spurring the development of several 400G Ethernet standards [1]. Frequency-dependent losses in copper interconnects limit their usefulness beyond ∼100 Gbps-m bandwidth-distance product [2], requiring alternative low cost energy-efficient approaches. While optical links are capable of satisfying the bandwidth and reach requirements, significant cost and power improvements over current deployments are necessary for their widespread adoption within the data center.