A 50Gb/s High-Efficiency Si-Photonic Transmitter With Lump-Segmented MZM and Integrated PAM4 CDR

The exponential growth of cloud computing and artificial intelligence asks for an ever-increasing communication bandwidth within the datacenter. Silicon photonics interconnect provides a promising way to achieve high-integration and low-power, which is essential for high-density hyper-scale datacenters. Among all electrical-to-optical (E/O) conversion solutions, the Mach-Zehnder modulator (MZM) outstands with wide optical bandwidth and high linearity, but suffers from the low modulation efficiency. To achieve 4-5dB extinction ratio (ER), 2-3 mm length phase shifters with traveling-wave (TW) electrodes are typically employed [1], [2]. However, the lossy electrode introduces significant attenuation at high frequency. Therefore, the TW-MZM requires higher drive-swing to obtain the same ER than the lumped modulator, which is hard for CMOS. To solve the problems, segmented MZM (SE-MZM) is proposed, consisting of multiple lumped capacitive segments [3], [4].