800G to 400G Breakout: How to Scale 400G Networks with 800G Ports

AI data centers can break one 800G switch port into two 400G logical links when the optics use compatible 100G-per-lane PAM4 signaling.

This breakout approach expands port count and bandwidth without requiring a full network refresh, making scaling easier for GPU clusters.

The tradeoff is hardware compatibility: OSFP, QSFP-DD, 112G SerDes, and the right 400G optics must align for the setup to work.

In practice, breakout can improve density, power efficiency, and economics for operators growing fast AI infrastructure.