FOUNDATIONS / STARTER NOTE
CPO, Optical I/O, and Silicon Photonics Are Not the Same Thing
A practical explanation of how these terms overlap, where they differ, and why the distinctions matter for architecture and product decisions.
Start with the layer each term describes
Co-packaged optics is a packaging architecture: it describes where optical engines sit relative to compute or switching silicon. Optical I/O is a system function: it describes moving information across a boundary using light. Silicon photonics is a technology platform: it describes how optical components can be integrated and fabricated.
A system may use silicon photonics without being co-packaged. A co-packaged design may implement optical I/O, but optical I/O also exists at other boundaries. Keeping these layers separate makes architecture reviews clearer and prevents a device technology from being mistaken for a complete product strategy.