A 4-Vppd160-Gb/s PAM-4 Optical Modulator Driver with All-Pass Filter-Based Dynamic Bias and 2- Tap FFE in 130-nm BiCMOS

This paper presents a high-speed, large-output swing driver with 2-tap feed-forward equalizer (FFE) for optical modulators in 130-nm SiGe BiCMOS process. A breakdown voltage (BV) doubler topology with all-pass filter (APF)-based dynamic bias is applied in the driver to improve the output swing and the bandwidth. A 2-tap fractional-spaced FFE is implemented to compensate for the insufficient bandwidth of optical modulators. Simulation results indicate that the driver achieves an output swing of 4 $\mathrm{v}_{\text{ppd}}$ and a 3-dB bandwidth of 62.4 GHz with a power consumption of 1.15 W. The performance of the driver is further evaluated in an electrical/optical (E/O) system where a Verilog-A model for Mach-Zehnder Modulator (MZM) with a 3-dB bandwidth of 35 GHz is used. Taking advantages of the 2-tap FFE, the E/O system achieves a 3-dB bandwidth of 50.4 GHz and can support 160-Gb/s PAM-4 optical communications.