84 GBd (168 Gbit/s) PAM-4 3.7 Vpp power DAC in InP DHBT for short reach and long haul optical networks

Abstract

The architecture and performances of a multilevel driver for pulse amplitude modulation (PAM) formats, designed and fabricated in 0.7 μm InP double-heterojunction bipolar transistor technology, are reported. The driver part is based on a power-DAC architecture which is integrated with the multiplexing stage composed of three 2:1 selectors. Up to 100 GS/s operation was validated and PAM-2, -4, -8 signals with high amplitude were measured. In particular, PAM-4 at 84 GBd and PAM-8 at 64 GBd operation was demonstrated with, respectively, a 3.7 and 4 Vpp differential output signal. This compact driver circuit is characterised by the highest merit factor in terms of high amplitude and the transmission capacity for an electronically generated multilevel signal.