At the Optical Fiber Communications Conference (OFC) 2024, Intel showed us a particularly interesting glimpse into the future of chip and interconnect design: the Optical Compute Interconnect (OCI) chiplet, which integrates photonics integrated circuits (PICs) and electrical integrated circuits (PICs) and electrical ICs. This chiplet is packaged with an Intel CPU and runs live data.

Intel believes this technology will be a game changer as it meets the growing demand for higher bandwidth over longer distances while consuming less power. Of course, the first applications are in AI infrastructure and HPC environments, where concerns about scalability across racks and clusters in large deployments are becoming increasingly apparent.

An Intel press release states: "By analogy, replacing electrical I/O with optical I/O for CPU and GPU data transfer is like moving from horse-drawn wagon deliveries with limited capacity and distance to using cars and trucks that can deliver large volumes of goods over much longer distances. The replacement of electrical I/O with optical I/O in data transfer is like moving from horse-drawn carriages with limited capacity and distance to cars and trucks that can deliver large volumes over much longer distances. It is this level of performance improvement and energy cost that optical I/O solutions such as Intel's OCI chiplets bring to AI scaling. This speaks volumes about where Intel sees the future of interconnect technology.

Although OCI is a prototype, it already supports bidirectional data transfer of up to 4 terabits per second (Tbps) over distances as far as 100 meters. Importantly, the technology is compatible with PCIe 5.0, making integration into existing PCIe-compatible infrastructure relatively easy. [In terms of power savings, Intel claims that its solution is much more efficient at only 5 pico-joules (pJ) per bit, compared to pluggable optical transceiver modules that consume only about 15 pJ per bit. [OCI chiplets can be integrated with future CPUs, GPUs, and SoCs. There is no reason to doubt the potential of this technology if it becomes widespread in the consumer segment in the next few years, and if it becomes widespread in the enterprise segment.

Imagine being able to mount a GPU that does not require a PCIe slot. It could be mounted anywhere in a compatible case and connected to the motherboard with cables without compromising performance. This could improve cooling performance and make motherboard design simpler (and cheaper).

Intel has developed a new silicon photonics manufacturing process and has stated that it expects this technology to scale from the 4 Tbps range to tens of Tbps in the future. Chips with optical interconnects and glass substrates are probably only one step closer.

Exciting!