Future of Optical Interconnect in AI Networking

Copper interconnects have dominated networking architecture for its low cost and reliability. However, as data rate and bandwidth scale, the reach of copper is limited to connections within the rack. As AI clusters grow and interconnect distances increase, the need for optical interconnects is inevitable. Optical interconnects have been widely deployed in front-end and AI scale-out networks where link distance limits the use case for copper interconnects. The next natural step of optical interconnect adoption would be applied to AI scale-up networks. This will usher in a new era of massive growth in optics consumption.

Key considerations for adopting optical solutions in AI scale-up networks include cost, power, escape bandwidth density, and reliability, which are benchmarked against copper interconnects. Silicon photonics (SiPh) is well positioned to address these considerations. Early data from the current generations of CPO have demonstrated power benefits for scale-out networks. With further CPO innovation and process node scaling, CPO power will approach those closer to copper interconnects. Furthermore, to address escape bandwidth density, incorporating multiple optical engines on the same xPU substrate, CPO will enable escape bandwidth up to 51.2Tbps.

Early deployments of SiPh-based CPO systems allowed multiple technology partners (OSAT, III-V, fiber) to work together to solve technical challenges. As more operational data (power, reliability) from these deployments come through, end-users are encouraged to accept CPO as viable platform for larger scale adoption.

In addition to SiPh solutions for scale-up, VCSEL-based multi-mode near-package optics (NPO) solutions offer an alternative for the near term.  Using a VCSEL based approach, interconnects can leverage on proven large-scale reliable manufacturing of multi-mode optics used in scale-out networks. 

In conclusion, SiPh solutions have reached a level of maturity to start the transition to large scale adoption needed in AI scale-up networks.

Key Technologies Covered

• High escape bandwidth density co-package optics (CPO) with xPUs
• High reliability manufacturing processes
• Large scale optical fiber management