Photonic switch fabrics in data center/high-performance computing networks

As introduced in Chapter 1, the world has witnessed the exponential growth of data traffic (doubling almost every 2 years) in warehouse scale data centers and large-scale high-performance computing (HPC) systems in the past few decades. Due to the increasing demands for various data intensive applications, such as video services, AI and machine learning, and cloud computing, the data center network had entered the so-called “Zettabyte (ZB) Era” with annual global traffic of 1.5 ZB in 2017 and this is expected to reach over 4.8 ZB per year in 2022. To serve the increasing traffic demands, the current trend has been driven toward mega-data centers with hundreds of thousands of servers for the benefits of economy of scale. On the other hand, the traffic flow of the data center/HPC networks has shifted from North–South to East–West, that is, the internal data traffic between servers and storages surpasses inbound or outbound data traffic. These trends pose unprecedented challenges to the intradata center interconnects in terms of bandwidth and connectivity.