As 400G fabrics become standard in modern data centers, the physical layer is no longer a secondary detail. Choosing between 400G DAC, AOC, and optical links directly impacts how fast you can scale racks, how dense you can build leaf–spine tiers, and how predictable your operations remain. The wrong mix can lock you into rigid layouts, unexpected power budgets, or expensive recabling projects later.

This page frames DAC, AOC, and optical transceivers as complementary tools for different distances, cable management models, and growth strategies. Instead of comparing specs in isolation, we focus on how ToR, leaf–spine, and inter-row designs influence the right choice of 400G direct attach, active optical cable, or pluggable optics, so architects can standardize link types while preserving flexibility for future capacity and topology changes.