Large Swing Optical Modulator Drivers for 100+ GBaud Applications

This thesis describes the design of a large-swing linear driver and a large-swing 90 GS/s digital-to-analog converter (DAC) with retiming in 55 nm SiGe BiCMOS technology, both with applications for next-generation optical transmitters. The linear driver’s measured differential gain is 20 dB and its small-signal bandwidth exceeds 70 GHz. Measured NRZ eye diagrams up to 120 Gb/s with 4.8 Vpp differential output swing are shown, as well as PAM-4 and PAM-8 eye diagrams up to 64 GBaud. The driver’s measured input linearity is −2.5 dBm (475 mVpp) per side. In simulation, the large-swing DAC demonstrates 90 GBaud PAM-4 with greater than 6 Vpp differential output swing. Its simulated effective number of bits (ENOB) is 3.51 at 90 GS/s.M.A.S