Design of a PAM-4 VCSEL-Based Transceiver Front-End for Beyond-400G Short-Reach Optical Interconnects
Jian He, Donglai Lu, Haiyun Xue, Sikai Chen, Han Liu, Leliang Li, Guike Li, Zhao Zhang, Jian Liu, Liyuan Liu, Nanjian Wu, Ningmei Yu, Fengman Liu, Xi Xiao, Yong Chen, N. D. Qi
Abstract
This paper presents a hybrid-integrated optical transceiver front-end for beyond-400G short-reach optical links. A pair of the monolithic 8-channel laser drivers and the trans-impedance amplifier (TIA) is developed in 180nm SiGe BiCMOS, incorporating arrayed Vertical-Cavity-Surface- Emitting Lasers and photo-detectors. The driver uses a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2^{\mathrm {nd}}$ </tex-math></inline-formula> -order continuous-time linear equalizer (CTLE) to compensate for the channel loss with a nonlinear frequency response. Both the inductive peaking and RC-degeneration are embedded at the output stage to extend the optical modulation bandwidth (BW). The series-peaking and multi-stage distributed CTLE are combined in a resistive feedback TIA topology for improved BW and linearity. Measurement results show up to 100-Gb/s PAM-4 electrical eyes of the driver and TIA. The optical transmitter front-end operates 56 Gb/s, 4.1-dB extinction ratio, and 6.6-pJ/bit power efficiency, while the optical receiver front-end achieves 56-Gb/s, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$10^{-6}$ </tex-math></inline-formula> bit error rate, and 5.9-pJ/bit power efficiency.