Abstract

A Wish List for OFC 2024 from LightCounting

OFC 2024 will include numerous demos of 224G technology and some of the first products based on it. We will refer to them as 200G per lane for simplicity and to avoid any confusion between 2024 and 224G. The industry is already starting to work on 448G (or 400G) per lane technology and we would love to see demos of those solutions as well.

New Photonics, a start-up from Israel, plans to share more details on their technology at OFC 2024. All we know for now is that it uses comb lasers to generate optical clock pulses and employs time domain multiplexing to produce 200G and 400G streams of data. We are looking forward to learning more about it and seeing its first.

Thin Film Lithium Niobate (TFLN) was a hot topic at OFC 2022 and this technology continues to make progress. AFR and Hyperlight will be presenting their latest achievements and hosting two events at the show. We hope to see TFLN modulators running at 400G per lane in PAM4 mode and 800G per wavelength with coherent detection.

Increasing data rates per lane is just one of the three possible directions to boost the bandwidth of optical interconnects. Higher lane speed is a preferred solution for most of the Ethernet and InfiniBand interconnects. Direct I/Os to accelerators, such as NVLink to Nvidia’s GPUs or ICI to Google’s TPUs, also need the highest lane speed possible. Nvidia is currently using parallel types of transceivers (SR8 and DR8), but it plans to use multi-wavelength solutions in the future as well. Google is already using 8-wavelength FR8 transceivers.

We expect more announcements from Innolume and Quintessent at the show. Both companies demonstrated multi-wavelength lasers and SOAs based on quantum dot (QD) technology. These devices offer superior reliability among many other benefits, which should have been noticed by potential customers. It is time to see demos of 8-wavelength FR8 transceivers with QD lasers inside.

Other types of connections to accelerators, such as PCIe and connectivity to High Bandwidth Memory (HBM), rely on a large number of lower-speed lanes to achieve Tbps levels of connectivity. All of these connections rely on either copper cables or copper traces today, but future designs will need optical connectivity, as discussed in our recently published report Optics for AI Clusters.

Several start-up companies are developing highly parallel optics for PCIe and HBM connectivity.

Avicena is well known by now with its micro-LED interconnects technology, but may reveal new products running at higher data rates or surprise us with customer announcements.

Nubis Communications disclosed its first designs of 16x64G optical engines for PCIe Gen6 at OFC 2023. The next product will support 112G per lane for PCIe Gen7 and that is what the industry really needs now.

Celestial AI disclosed some of its plans which were tightly guarded until recently behind an enigmatic company name. The plans are ambitious and resemble the Trojan horse strategy pioneered two millennia ago with a 21st-century twist. Celestial AI’s IP allows the optics to be hidden in a substrate or an interposer with 2.5D packaging under a GPU chip. The GPU would not know what is coming until night falls and it is too late. The only way for the GPU to send the data out will be via optics and the victory will be declared soon after that.

Linear Drive Pluggable transceivers were the highlight of OFC 2023 and it will remain a hot topic this year. We also expect to see more progress with linear drive co-packaged optics (CPO). What would be really cool to see is the first deployments of one of both of these solutions in AI clusters.

LightCounting will once again moderate a panel discussion at the tradeshow with Andy Bechtolsheim as the main attraction: “Next Generation Optical Interconnects for AI Clusters: Beyond Linear Drive Optics”, Tuesday, March 26^th, 10:45-11:45 in Theater II. Ranovus will be also participating in the panel discussion and we expect more announcements from them on CPO.

Yet, the best part of every OFC is something unexpected. New companies, technologies, products and research results are always fun to see. This really belongs at the top of our wish list!