Choosing the Right Data Center Cabling Solution: AOC or DAC?
As AI and Big Data drive explosive growth in computing demand, data centers require high-performance, low-latency connectivity. Here’s how to select between Active Optical Cables (AOC) and Direct Attach Copper Cables (DAC) for optimal server interconnects.
Key Connectivity Requirements in Modern Data Centers
- High-Speed Computing
- AI training demands GPU/accelerator clusters with 100G+ bandwidth
- Real-time inference requires <1μs latency between servers
- Scalable Bandwidth
- Big Data workflows need 25G/100G/400G adaptable links
- Storage networks require lossless RoCE/RDMA support
- Space & Power Efficiency
- TOR (Top-of-Rack) deployments need compact, low-power cabling
DAC: The Cost-Effective Short-Reach Solution
Best For: Server-to-switch links ≤3m
✅ Advantages:
- Lowest Cost: 60-70% cheaper than AOC (no optical components)
- Zero Latency: Electrical signal direct transmission
- Plug-and-Play: No additional power required
⚠ Limitations:
- Max 7m reach (400G DAC)
- Higher weight (copper) may strain ports
Typical Use Cases:
- Same-rack server interconnects
- Leaf-spine connections in hyper-converged infrastructure
AOC: The High-Performance Long-Distance Choice
Best For: 3m-100m high-bandwidth links
✅ Advantages:
- Longer Reach: Up to 100m (400G AOC)
- Lighter Weight: 80% less bulk than DAC
- EMI Immune: Optical transmission avoids interference
⚠ Limitations:
- 20-30% higher cost than DAC
- Requires minimal bend radius (30mm)
Typical Use Cases:
- Cross-rack AI/GPU cluster connections
- High-density spine-leaf architectures
- Disaster recovery site links
Technical Comparison
|
Feature |
DAC |
AOC |
|
Max Distance |
3-7m (400G) |
30-100m (400G) |
|
Latency |
0.1ns/m |
5ns/m |
|
Power Draw |
0W |
1-2W per end |
|
Weight |
500g/m (400G) |
100g/m (400G) |
|
Cost (400G) |
150−150−300 |
400−400−600 |
Selection Guidelines
- Choose DAC When:
- Connecting servers within same rack
- Budget is primary constraint
- Operating in low-EMI environments
- Choose AOC When:
- Spanning multiple racks/cabinets
- Future-proofing for 800G/1.6T upgrades
- Deploying in high-RF zones (e.g., near power systems)
Future-Proofing Considerations
- 800G Ready: AOC supports smooth migration to next-gen speeds
- Thermal Management: DAC may require airflow optimization in dense racks
- Smart Cabling: New AOC variants integrate health monitoring sensors
Pro Tip: For hyperscale AI clusters, deploy DAC within racks and AOC for spine connections to balance cost/performance.