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].

[1]  Enrico Temporiti,et al.  22.9 A 1310nm 3D-integrated silicon photonics Mach-Zehnder-based transmitter with 275mW multistage CMOS driver achieving 6dB extinction ratio at 25Gb/s , 2015, 2015 IEEE International Solid-State Circuits Conference - (ISSCC) Digest of Technical Papers.

[2]  Jingbo Shi,et al.  A 50-Gb/s PAM4 Si-Photonic Transmitter With Digital-Assisted Distributed Driver and Integrated CDR in 40-nm CMOS , 2020, IEEE Journal of Solid-State Circuits.

[3]  Vishal Saxena,et al.  A 3D-Integrated 56 Gb/s NRZ/PAM4 Reconfigurable Segmented Mach-Zehnder Modulator-Based Si-Photonics Transmitter , 2018, 2018 IEEE BiCMOS and Compound Semiconductor Integrated Circuits and Technology Symposium (BCICTS).

[4]  Hao Li,et al.  A 32Gb/s NRZ, 25GBaud/s PAM4 reconfigurable, Si-Photonic MZM transmitter in CMOS , 2016, 2016 Optical Fiber Communications Conference and Exhibition (OFC).