Lightmatter is producing a 4,000 mm2 interposer integrating a waveguide network and 1,024 serdes, and the company has also announced a copackaged optics (CPO) technology enabling 200 Tbps of total bandwidth per package. Lightmatter plans to offer the Passage M1000 reference interposer this summer and sample the Passage L200 CPO product next year. Targeting network switches and data-center processors (XPUs), the M1000 and L200 stand out for connecting to chiplets across their surface instead of only at their edges, helping increase connectivity and shrink packages.
Concern that copper can’t handle ever-rising interconnect speeds is heightening interest in photonics. Optical interposers are a Chips Act funding opportunity, and Lightmatter is far along in commercializing them. The Passage M1000 connects chiplets stacked atop it and provides 256 fiber attachment points.
Several companies are pursuing CPO, with Nvidia the most recent to join the fray and Broadcom the furthest along regarding production. The Lightmatter Passage L200 provides 32 Tbps of combined transmit and receive bandwidth over 40 fibers. For comparison, Broadcom’s CPO design employs 6.4 Tbps engines, delivering the same per-fiber bandwidth but requiring more I/O chips per package. The faster L200X doubles the per-fiber bandwidth to 1.6 Tbps.
We expect gradual adoption of advanced optical technologies as new ways to extend copper’s life emerge. Provided they deliver economic as well as technical advantages, Lightmatter’s innovative optical interposer and CPO approach, however, will accelerate the transition and help XPUs to continue scaling.