InP DHBT 200-GSa/s Large Output Swing AMUX-Driver Using Transimpedance Stage Loading for 200-Gbaud-and-Beyond Optical Transceivers

In this article, we report on the design and characterization of InP-DHBT analog multiplexer (AMUX)-driver integrated circuits (ICs) for next generation $\geq 200$ Gbaud (GBd) metro/long-haul optical transceivers. We show that the transimpedance stage (TIS) loading of the AMUX selecting cell provides superior gain $\times $ bandwidth and linearity performances with respect to the commonly used resistive and cascode loads. Moreover, the driving clock amplitude and tail current of the selecting core are shown to be key parameters for the AMUX-driver design. The AMUX-drivers with TIS loading are fabricated in the III-V Lab’s InP DHBT process, showing up to 200-GSa/s sampling rate, without any support of DSP. At 100 GSa/s and 2.4 Vppd of PAM-4 output swing, the highest AMUX FoM is obtained. To the best of the authors’ knowledge, these are the highest performances reported to date for an AMUX(-driver). Additionally, an AMUX-driver chip is assembled with a TFLN modulator, demonstrating an E/O bandwidth in excess of 85 GHz, while supporting the generation of 100-GBd PAM-4 optical signals, without DSP or active cooling.