30.6 A 6V Swing 3.6% THD >40GHz Driver with 4.5× Bandwidth Extension for a 272Gb/s Dual-Polarization 16-QAM Silicon Photonic Transmitter

Abstract

Traditionally, the high-performance optical coherent communication TX has been a discrete assembly based on LiNbO 3 modulators and III-V drivers. While delivering high bandwidth (BW) and linearity, such a platform is bulky and does not work for high-volume or intra-datacenter applications. Silicon photonics (SiPh) offers a Si-based platform for next-generation transceivers by integrating all required optical functions. But even in existing SiPH-based commercial modules, the driver generally remains a III-V-based chipset, impeding the path to an all-silicon solution. The challenge for an all-silicon-based coherent optical TX is in the simultaneous requirement of high differential voltage swing (V ppd ), linearity and BW. In this work, we present a 130nmSiGe driver achieving a 6V ppd swing, 3.6% THD and small-signal BW over 40GHz. Co-packaged with a SiPh transceiver, the driver enables the same level of performance as LiNbO 3 modulators with III-V drivers and demonstrates 272Gb/s dual-polarization (DP)-160AM transmission. This is enabled using (1) circuit techniques that achieve a BW extension ratio (BWER) of $4.5\times $ for the Mach-Zehnder modulator (MZM) driver while simultaneously achieving large swing ($\mathrm {V}_{\mathrm {p}\mathrm {p}\mathrm {d}}$=6V), high linearity (THD $=3.6$%) and mitigating breakdown voltage (BV) and reliability concerns with large V ppd ; (2) pre-emphasis control in the driver output stage and gain control in the pre-driver VGA to compensate for the electro-optic (E/0) BW of the TX over corners; and (3) a monolithic integration of MZMs with a polarization rotator (PR) optimized for high-BW, low-crosstalk and co-integration with drivers for DP-OAM and DP-OPSK operation.