An 8.2-pJ/bit, 56 Gb/s Traveling-wave Modulator Driver with Large Reverse Terminations

This paper presents a 56 Gb/s traveling-wave Mach-Zehnder Modulator (TW-MZM) driver fabricated in the GlobalFoundries 8XP 130-nm SiGe BiCMOS process employing a cascode topology. The quasi-open collector design delivers a 4.4
${{\mathrm{V}}_{\text{pp}}}$
differential swing and reduces the amplitude of the secondary reflections while maintaining a low overall power consumption of 460 mW, or 8.2 pJ/bit at 56 Gb/s, including the modulator termination resistance dissipation. The driver has two variants, each of which provides a different TW-MZM biasing scheme, to enable operation at two different PN junction phase shifter biases. Eye-diagrams at up to 60 Gb/s are presented as well as bit-error rate (BER) bathtub curves.