Understanding In-Package Optical I/O Versus Co-Packaged Optics

By  Vladimir Stojanovic, Ayar Labs

Though the two terms above are often compared, one is a replacement strategy for pluggables while the other is a chiplet-based optical interconnect solution. A closer look at both will help clarify.

Recent advancements in silicon photonics are upending the optical market in the data center, with significant ramifications for how future AI, cloud, and high-performance computing systems will be designed, architected, and deployed. The core problem involves how to best connect compute chips over longer distances while maintaining bandwidth, energy, and density metrics that are acceptable for a given application.

At the same time, there is a lot of confusion — some inadvertent, some perhaps intentionally sown — regarding the differences between interconnect technologies such as co-packaged optics (CPOs), pluggables, and in-package optical I/O. Moreover, various industry standards are in play for these optical connections: What do they portend for the future?

Let’s start with some technology basics. For those unfamiliar with silicon photonics, it is a way to implement optical components in a silicon integrated circuit process, leveraging the semiconductor economies of scale to create photonic integrated circuits (PICs) that use light to transmit and process data. As with optical networking writ large, these PIC components can overcome many of the limitations of traditional copper-electrical connections to improve the bandwidth, latency, energy efficiency, and reach of signals within the data center.
 

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