High-Speed SiGe BiCMOS Circuits for Optical Communication

This paper presents an overview of SiGe BiCMOS circuits for next-generation optical communication links targeting 100 GBd PAM4 modulation per wavelength to support 4-lane 800Gb and 8-lane 1.6Tb Ethernet. Signal generation at these rates is challenging. For this, an analog multiplexer making use of return-to-zero (RZ) modulation is presented. The explicit RZ generation enables equalization of the interleaved signal. Higher equalization orders are obtained with a 120 GBd PAM4 4-to-1 multiplexer with a mixed-signal 7-tap feedforward equalizer. The equalizer consists of a combination of digital delay cells and analog delay cells enabling a compact and power efficient solution. Quad-channel modulator drivers and receivers finish the required high-speed circuits. Based on traveling-wave architectures high gain-bandwidth products are realized.