DAC vs. AOC vs. AEC: Which Cable Goes Where in an AI Rack?
Short version: use passive DAC for connections within a rack or between adjacent racks (under roughly 3 meters), AOC when you need to cross rows or halls at higher speeds without the power draw of full optics, and AEC as a middle ground that extends copper's reach a few extra meters at lower power than optical. The right choice depends on distance, power budget, and how often the link will be serviced — not just raw bandwidth.
The Three Options at a Glance
| Type | Typical Distance | Power Draw | Relative Cost | Best For |
|---|---|---|---|---|
| DAC | Up to ~3m | Near-zero | Lowest | In-rack, adjacent-rack |
| AEC | ~3-9m | Low | Moderate | Borderline runs, power-conscious builds |
| AOC | 10m+ | Higher | Highest | Row-to-row, hall-to-hall |
DAC — Direct Attach Copper
- Near-zero latency, near-zero power draw
- Best for server-to-ToR, in-rack, and adjacent-rack runs
- Limitation: distance ceiling, and cables get bulkier/stiffer at higher lane counts
AEC — Active Electrical Cable
- DSP-based signal conditioning extends copper's reach without going optical
- Good middle ground for rows that are "almost" DAC range
- Newer technology, fewer SKUs currently on the market
AOC — Active Optical Cable
- The only practical option beyond ~10 meters at high speed
- Higher cost and power draw, but a slim profile and no distance-based signal loss
- Trade-off: factory-terminated length can't be field-adjusted, and a failure means replacing the whole cable, not just a module
How to Decide for Your Build
A simple way to think about it: if your link is under 3 meters and stays inside a rack, reach for DAC. If it's row-to-row or hall-to-hall, you need AOC. If you're right on the edge and want to save on power, AEC is worth a look.
FAQ
Can I mix DAC and AOC in the same cluster?
Yes — most production clusters use a mix, matching cable type to the specific link's distance and role rather than standardizing on one type throughout.
Is AEC compatible with the same ports as DAC/AOC?
Generally yes, using the same QSFP/OSFP form factors, but always confirm port compatibility with your specific switch and NIC before ordering.
Which is cheaper, DAC or AOC?
DAC, significantly — but AOC's role at longer distances isn't replaceable by DAC, so the comparison is about fit, not just price.
Related Hardware / You Might Also Need
Now that you know which cable type fits your run, here's where to find it:
- Shop DAC Cables — for in-rack and adjacent-rack connections
- Shop AOC Cables — for row-to-row and hall-to-hall runs
- Browse All Interconnects — transceivers and additional AOC/DAC options in one place
Ready to Buy?
Not sure which spec fits your exact switch and NIC combination? Our team can confirm compatibility before you order.
Shop DAC Cables | Shop AOC Cables | Talk to a Hardware Specialist