| Factor | DAC | AOC |
|---|---|---|
| Medium | Twinax copper | Optical fibre with active electronics |
| Typical use | Same rack / adjacent rack | Longer short-reach links where copper DAC is unsuitable |
| Separate optics | No | No |
| Electrical isolation | No | Yes, across the optical portion |
| Power/thermal | Generally low for passive DAC, but cable assembly limits apply | Active ends consume power |
Passive DAC
Passive DAC uses copper twinax with SFP+ ends. It is attractive for short, fixed interconnects because there are no separate optical transceivers and the assembly is simple. Length limits and supported host combinations should be taken directly from the cable vendor and switch/NIC documentation.
AOC
An active optical cable contains optical conversion at the ends. It can extend farther than passive copper DAC while remaining a single assembly. It is useful when an SFP+ link is short enough for an AOC but not convenient for twinax.
Compatibility
Switches and NICs can enforce vendor coding or supported-cable lists. A physically identical-looking SFP+ DAC/AOC may not be accepted by every platform. Check supported transceiver/cable part numbers before ordering large quantities.
When to use structured fibre instead
If the link needs to pass through patch panels, buildings, floors or a future-proof fibre plant, a conventional optical transceiver plus structured fibre is usually easier to document and maintain than a cable assembly. DAC/AOC is best treated as an equipment interconnect.