DC-to-89-GHz AMUX-based IQ Modulator in 250-nm InP HBT Technology for Multiplexing-DAC Subsystem

This paper presents an ultra-broadband in-phase and quadrature (IQ) modulator in 250-nm InP heterojunction bipolar transistor (HBT) technology for a multiplexing-DAC subsystem enabling high-symbol-rate baseband signal generation in optical communications. The IQ modulator consists of two analog multiplexers (AMUXs), data/clock buffers, a quadrature filter, a linear adder, and an output buffer. The fabricated AMUX-based IQ modulator IC has a bandwidth of 98 GHz ranging from direct current (DC) and consumes a total power of 880 mW with a supply voltage of −4.0 V. The packaged IQ modulator module with coaxial connectors maintains a bandwidth of 89 GHz. Using the multiplexing-DAC subsystem based on this module, high-symbol-rate baseband signal generations and optical modulations up to 168-GBaud 16-ary quadrature amplitude modulation (16QAM) were successfully demonstrated. To the best of the authors’ knowledge, this is the broadest bandwidth IQ modulator reported to date.