UC Santa Barbara

Data centers are the pillars of modern internet infrastructure that have enabled the proliferation of emerging cloud applications, social media, and artificial intelligence, among others that are becoming increasingly integrated into our everyday lives. As data center traffic continues growing at a compound annual growth rate exceeding 25\% with internal server-to-server traffic accounting for well over 70\% of the total, engineering increased capacity through optical intra-data center interconnects (IDCIs) is essential. In keeping up with capacity demands, energy efficiency improvements are required conserve the data center energy footprint. The performance of IDCIs are thus primarily characterized by two metrics: capacity defined in bits-per-second and energy efficiency defined as the cost of energy-per-bit.

This dissertation will broadly cover the design and measurement results of energy-efficient front-end receiver integrated circuits (RXICs) and transmitter integrated circuits (TXICs) for high data rate IDCIs.

In Part I of this thesis, a comprehensive benchmarking approach for optical receivers with implications for link power consumption in both direct and coherent detection-based links will be introduced. For direct detection links, RXIC designs operating up to 64 Gbps at less than 2.53 pJ/bit will be presented and compared with the state of the art. For coherent detection links, an I-Q Costas-based optical RXIC operating up to 100 Gbps at less than 5.34 pJ/bit will be discussed and compared to the state-of-the-art. The RXICs are implemented in 130 nm SiGe HBT technology.

Part II of this thesis will investigate the energy efficient implementations of two-tap feedforward equalizers (FFEs) for high-speed optical TXICs in direct- and external-modulation schemes. For directly modulated, Vertical Cavity Surface Emitting Laser (VCSEL) transmitters, a TXIC implemented in 130 nm SiGe HBT technology is reported for data rates up to 60 Gbps at an energy efficiency less than 2.85 pJ/bit. For externally modulated, Mach Zehnder Modulator (MZM) transmitters, a TXIC implemented in 45 nm CMOS SOI technology is reported for data rates up to 80 Gbps at an energy efficiency less than 3.9 pJ/bit.