A 51Gb/s, 320mW, PAM4 CDR with baud-rate sampling for high-speed optical interconnects

A quarter-rate 51Gb/s PAM4 CDR with decoded dual-NRZ outputs is presented for 400GbE optical transceivers. A baud-rate data-only sampling PD with zero-crossing integrating front-end is proposed to minimize the clock generation and distribution overhead, as well as improving the noise resilience under PAM4 low-SNR inputs. Measurement results show the CDR features 1.08ps RMS clock jitter, 3.4×10
^-9
PAM4 data recovery BER, and 6.27pJ/bit power efficiency.