Faced with an increasing need to support platform flexibility, higher density, and better utilization, data center infrastructure designers are moving toward data center disaggregation. In a disaggregated architecture, homogeneous resources (storage, compute, networking, etc.) are connected via optical interconnects. One of the advantages of this type of architecture is that no resources are wasted. A workload will come in needing x amount of storage, y amount of compute, and z amount of networking resources. A central intelligence unit determines and takes what is needed from each of the boxes and nothing more, with the optical interconnects providing the highways on which the data travels. Remaining resources are freed up for other workloads. By contrast, with a hyperconverged server, all of the storage, compute, and networking resources for a given job are locked in, regardless of how much is actually needed for the workload. So, some of the resources could be wasted.
Copper interconnects have played a central role in networks for their high conductivity, low cost, flexibility, and heat resistance. These days, copper is mainly found within server racks. The increase in network speeds has also triggered an increase in the power and bandwidth needed to drive data signals reliably over long runs of copper cables. This trend has paved the way for optical interconnects, which have become the star of the show in rack-to-rack, room-to-room, and building-to-building configurations. Because they transmit signals via light, optical interconnects support higher bandwidth and speeds as well as lower latency and power than their metal counterparts, making them ideal for disaggregated data center applications.
Optical interconnects also facilitate network infrastructure upgrades to take advantage of newly introduced technologies, such as those supporting 400G, 800G, and 1.6T Ethernet. This convenience comes by way of the pluggable optical modules that connect to optical cables. These modules provide a relatively easy and flexible way to connect the optical fiber cables to network equipment.
Data network speeds are continuing to go up. As networking speeds increase beyond 400 Gbps, the power needed to drive the electrical signals to the modules becomes a concern. This is where co-packaged optics answer the call. Co-packaged optics consist of a single package integration of electrical and photonic dies. Traditionally, the electrical and photonic components are implemented via pluggable modules—devices connected on the edge of the PCB in the face of the server rack. But the move—and requirements for—miniaturization mean that having everything in a single package is much more feasible. The electrical link between the host SoC and the optical interface will become much shorter (and, thus, lower power) if it connects to co-packaged optics in the package versus to a pluggable module in the faceplate of the rack.