GoKawiilThe requirements of AI clusters have made optical interconnections practical for scale-out connectivity, but as bandwidth requirements increase, optical connectivity is becoming viable for scale-up connections. As a result, the industry is moving optical interfaces closer to CPUs and GPUs, from the front-panel transceiver to the package itself through co-packaged optics (CPO), and eventually directly into the processor package.
Optical connectivity has been used for decades, as electrical links cannot efficiently and reliably transmit data over long distances at high data transfer rates. However, the cost and complexity of optical components limited their use to long-reach connections.
The importance of CPO is rising because electrical interconnects are no longer scaling as quickly as AI processors, and feeding thousands of accelerators within a data center requires an exponential increase in communication bandwidth. In a traditional optical networking architecture, the processor or switch ASIC communicates electrically with a pluggable optical transceiver located at the front panel of a server or switch. However, as signaling speeds climb to 200 Gb/s - 400 Gb/s per lane and beyond, transmitting electrical signals over long copper PCB traces on a motherboard becomes increasingly inefficient due to higher insertion loss, greater power consumption, and tighter signal integrity requirements.
Latest Videos From Tom's Hardware Watch full video here:
While technically possible, it demands the use of better materials, retimers, complex compensation processing, and equalization circuitry, which increases the cost of server infrastructure and its power consumption. CPO moves optical engines next to the processor or switch ASIC to shorten the electrical path before signals are converted into light, which means lower power consumption per transmitted bit, increased bandwidth density, and predictable scalability. As a result, CPO is increasingly viewed as a necessary technology for next-generation AI infrastructure.
Because AI is viewed as a major megatrend, CPO is set to become ubiquitous; there are dozens of companies working in the CPO ecosystem, including foundries, OSATs, optical I/O startups, laser manufacturers, fiber suppliers, packaging houses, and networking vendors.
As there are so many vendors pursuing different goals with different strategies, for this story, we are going to limit ourselves only to companies that actually produce things and whose roadmaps reflect their technological capabilities. So far, only four foundries have publicly articulated meaningful CPO manufacturing strategies: Intel Foundry, GlobalFoundries, Samsung Foundry, and TSMC.
The four companies each represent four different CPO strategies and have very distinct plans for the future, so their plans and capabilities may not be directly comparable. Nonetheless, reviewing their offerings gives us an idea about where the industry is going from the perspective of actual foundries.
TSMC: COUPE for everything
TSMC has historically been absent from the optical connectivity market as a product supplier. However, having worked on silicon photonics for many years, it now has the broadest ecosystem and manufacturing roadmap with its Compact Universal Photonic Engine (COUPE).
... continue reading