DAC vs AOC: Picking the Right Short-Reach Cable for Your Rack

What "DAC" and "AOC" actually mean

Both are end-to-end pre-terminated cable assemblies with built-in pluggables — you don't pick separate transceivers and patch cords.

• DAC (Direct Attach Copper) — twinaxial copper between two SFP/QSFP

plugs. Passive variants do no signal regeneration; active variants embed a re-driver to hit longer reaches.

• AOC (Active Optical Cable) — multi-mode fiber between two pluggables

that contain a VCSEL transmitter and PIN receiver. Optical, but cheaper than buying transceivers + fiber separately.

Reach and cost crossover

Within a single rack (≤ 5 m), passive DAC is unambiguously the right answer — lowest cost, lowest latency, zero power. The moment you cross racks or rows, AOC becomes preferable; weight and bend radius of copper twinax at 100 G+ become installer pain points.

When to skip both and use transceivers + fiber

Rack-to-rack distances that vary per deployment, future-proofing for transceiver upgrades, or environments where the same fiber plant must survive multiple generations of speeds.

We stock DAC and AOC in 10 G / 25 G / 40 G / 100 G — get in touch for 400 G QSFP-DD and 800 G OSFP variants.