What's CPO and the ecosystem
Optical I/O, Co-Packaged Optics (CPO), and Traditional Interconnects Migration from Copper to Optics in Switch ASICs 1. Introduction As bandwidth demands scale into the multi-terabit era, traditional electrical interconnects on PCBs are hitting fundamental limits in power, signal integrity, and reach. This has driven the emergence of: Pluggable optics (today’s standard) Co-Packaged Optics (CPO) Full Optical I/O (integrated photonics) While the transition is already underway in switch ASICs, GPUs/TPUs follow a different trajectory due to architectural differences. 2. Three Interconnect Architectures 2.1 Traditional Pluggable Optics Architecture: ASIC sends high-speed electrical signals (SerDes) Signals travel across PCB (long traces) Reach pluggable module (QSFP/OSFP) Converted to optical and transmitted via fiber Key Characteristics: Long electrical paths (10–30 cm or more) High power consumption Signal integrity challenges Mature ecosystem Mental Model: Chip → long copper → opti...