Photonics startup Mixx aims to replace copper with light in large-scale graphics processor clusters. Founded in 2023 by Vivek Raghuraman and Rebecca Schaevitz, it has unveiled a first product, the SxC connector, which bundles 64 optical fibers into a single component. Its roadmap also covers optical engines, optical switches, and control software.
Modern racks, like Nvidia’s NV72, rely on numerous copper cables that allow six dozen or more GPUs to operate as a single unit. With the planned expansion of these communication domains, the move to optics becomes inevitable, but the number of fibers at the back of racks also increases. This is the first problem Mixx intends to solve. “We can place 1,000 fibers in 800 mm²,” Vivek Raghuraman told The Next Platform.
Beyond connection density, Vivek Raghuraman believes the rise of these large compute domains forces a rethink of system construction, with a rack backplane serving as an optical interposer for chips. Freed from copper constraints, he sees a path to a fully optical compute fabric. To achieve this, Mixx is developing near-package optics (NPO) and co-packaged optics (CPO) engines, optical circuit switches (OCS), and a software control plane. “It’s a three-part roadmap we are developing to enable optical scale-up networks,” he specified.
The path will be long. Vivek Raghuraman worked for seven years at Intel, where his team achieved several silicon photonics breakthroughs, and he contributed to the development of Broadcom’s CPO optical switches. “We are not just making proof-of-concept solutions, but something that can be deployed by hyperscalers,” he said. Mixx will therefore time its product releases to market demand.
Nvidia adds light between racks
With its Vera Rubin Ultra systems, Nvidia extends its NVLink Switch networks from 72-144 to 576, then to 1,152 GPUs, thanks to optics. Communications within each rack will remain copper, while those between racks will use light. Nvidia has not yet detailed how this works.
According to an estimate by The Next Platform, assuming one fiber pair per SerDes (the component that serializes and deserializes data), the Vera Rubin NVL576 system would require about 20,736 fiber pairs to connect the eight NVL72 racks that comprise it, or 2,592 pairs per rack. Nvidia could reduce this number using dense wavelength division multiplexing, which sends multiple wavelengths through a single fiber, but even with 16 wavelengths per fiber, the volume remains significant. This is why Mixx is starting with the connector. According to the article, Mixx plans to commercialize its first NPO module in 2028 or 2029, and its CPO product towards the end of the decade, when SerDes would no longer be viable for scale-up.
