DAC vs AOC: when and why to choose?

• A. DAC for short (<3-5 m) cost-effective copper runs; AOC for longer runs with EMI immunity.
• B. DAC for long runs; AOC for short runs.
• C. DAC uses fiber; AOC uses copper.
• D. DAC for short (<3-5 m) cost-effective copper runs; AOC for longer runs with EMI immunity.

Answer: (D)

Direct Attach Copper is the cost-effective way to connect devices over copper for very short distances, because copper cables are cheap and simple but lose signal quality quickly as length increases. Active Optical Cable uses fiber with integrated electronics, so it can carry signals over much longer distances and is immune to EMI and cross-talk. In practice, you’d pick DAC for short (<3–5 meters) copper links to keep costs and latency down, and choose AOC for longer runs where EMI immunity and greater reach are important. The tradeoffs are that AOC is more expensive and involves fiber infrastructure, while DAC is cheaper but limited in how far it can reliably go.