Radix-expanded densely-spaced WDM technology for co-packaged optics switches

Optical interconnects are a core technology for scaling AI/ML networks by linking NPU/GPUs directly or through ethernet switches with each other. With switch and link capacities doubling every 2 years, CPO (co-packaged optics) and OIO (optical Input/Output) connectivity solutions are emerging for tackling multiple challenges simultaneously: Reduction of power consumption and latency, and the increase of shoreline bandwidth density. In this work we explore the scaling limitations of DR-based (Direct Reach, parallel fiber output) CPO devices and demonstrate how densely-spaced WDM CPO variants can overcome this bottleneck, while simultaneously supporting a maximum switch radix, within the framework of Horizon Europe project ADOPTION. We demonstrate the first generation of (de-)multiplexer technology and their impact on transmission quality and network architecture.