High-Speed Ultralow-Power Hybrid Optical Transmitter Module With InP I/Q-SEMZM and BiCMOS Drivers With 4-b Integrated DAC

A hybrid optical transmitter module comprising a 15-segment InP in-phase/quadrature-phase segmented Mach-Zehnder modulator and two SiGe:C BiCMOS drivers featuring integrated 4-b digital-to-analog converter functionality is described. The drivers, fabricated in the 0.13-μm process of IHP, deliver a differential output voltage of 2.5 V pp across all the 15 segments while dissipating less than 1 W of power each, at the maximum. Clear electrical eye diagrams up to 40-Gb/s from every output are reported. The module allows a wide range of modulation formats, among which up to eight-pulse amplitude modulation and polarization-division-multiplexed (PDM) 64-quadrature amplitude modulation (QAM) back-to-back error-free electro-optical transmission at a record speed of 32 GBd are demonstrated. The 32-GBd PDM 64-QAM signal was transmitted error-free over 80 km of standard single-mode fiber, featuring 7.8-pJ/b energy consumption. The devised hybrid arrangement proves the suitability of SiGe HBT drivers for achieving higher speeds over their CMOS counterparts, with comparable low power dissipation, for advanced optical transceivers.