Why AI Data Centers Depend on DAC and AOC High-Speed Interconnects

With the rapid growth of AI computing, data centers are transforming from storage-centric architectures into compute and interconnect-driven infrastructures.

Whether for large-scale AI model training clusters or inference platforms, high-speed, low-latency connectivity has become a critical factor determining overall system performance.

Among various networking solutions, DAC (Direct Attach Copper) cables and AOC (Active Optical Cables) have become essential components for modern AI data center infrastructure.

1. The Core Challenge of AI Data Centers: Beyond Computing Power

In the past, GPU and CPU performance were considered the primary factors determining computing capability. However, in real-world AI clusters, another critical challenge has emerged:

Data transmission speed often cannot keep pace with computing performance growth.

During large-scale AI model training, such as thousands of GPUs operating in parallel, frequent parameter synchronization through All-Reduce communication is required.

If network bandwidth is insufficient or latency is too high, it can directly result in:

• Reduced GPU utilization

• Longer AI model training time

• Increased energy consumption

This is why the concept of “Network is the Computer” is being revalidated in the AI era.

2. DAC and AOC: Two Core Interconnect Solutions for AI Networks

2.1 DAC (Direct Attach Copper) Cable

https://www.c-light.com/products/AOC_DAC/DAC.html

DAC is a low-cost, low-power short-distance interconnect solution, mainly used for connections within the same rack or between adjacent racks.

Key Advantages:

• Ultra-low latency with no active optical components

• Extremely low power consumption without optical-electrical conversion

• Significant cost advantages

• High reliability

Typical Applications:

• ToR switch ↔ Server connections

• Internal GPU server interconnects

• Short-distance high-speed connections (≤3–5m)

• 10G / 25G / 100G / 400G networking

In AI clusters, DAC serves as the high-density and cost-efficient connectivity foundation.

2.2 AOC (Active Optical Cable)

https://www.c-light.com/products/AOC_DAC/AOC.html

AOC integrates optical transceiver components inside the cable assembly, converting electrical signals into optical signals for longer-distance transmission.

Key Advantages:

• Longer transmission distance (up to 100m+)

• Strong resistance to electromagnetic interference

• Higher bandwidth scalability (supporting 400G, 800G, and beyond)

• Suitable for complex data center cabling environments

Typical Applications:

• Rack-to-rack interconnects in Leaf-Spine architectures

• Cross-rack GPU cluster communication

• High-speed switch-to-switch connections

AOC acts as the high-bandwidth bridge for medium-distance AI data center interconnects.

3. Why Do AI Data Centers Rely on DAC and AOC?

3.1 Meeting Extreme Bandwidth Requirements (100G → 400G → 800G)

AI workloads are driving exponential growth in network bandwidth requirements.

Examples:

• Large AI model training requires Tbps-level throughput

• GPU-to-GPU communication requires non-blocking networks

DAC and AOC solutions support current and future high-speed standards, including 400G and 800G connectivity, making them practical solutions for next-generation AI networks.

3.2 Reducing Power Consumption and Cooling Pressure

AI data centers are already facing enormous power and thermal challenges.

High-power interconnect solutions can further increase operational costs.

Advantages:

DAC:

• Almost zero additional power consumption

AOC:

• Lower energy consumption compared with traditional optical transceiver + fiber solutions

At large deployment scales, this directly impacts TCO (Total Cost of Ownership).

3.3 Simplifying Deployment with Plug-and-Play Connectivity

Compared with traditional optical transceiver and fiber patch cord solutions:

DAC and AOC provide:

• Integrated cable solutions

• No additional configuration requirements

• Fewer potential failure points

For massive AI clusters with thousands of network ports, simplified deployment and maintenance are extremely important.

3.4 Supporting High-Density GPU Cluster Architectures

Modern AI data centers commonly adopt:

• Spine-Leaf network architectures

• GPU POD architectures

• Large-scale parallel computing clusters

These architectures share one common characteristic:

A dramatic increase in interconnection requirements.

DAC enables high-density short-distance connections, while AOC provides flexible expansion between racks.

Together, they achieve:

• Optimized cost

• Maximum performance

• Flexible network architecture

3.5 The Best Balance Between Cost and Performance

DAC and AOC provide the optimal balance between performance, scalability, and deployment cost for AI data centers.

4. Future Trends: The Era of 800G and Beyond

As AI models continue to expand in scale, interconnect technologies are also evolving rapidly.

Future trends include:

• Wider adoption of 800G DAC and AOC solutions

• Silicon Photonics enabling higher integration levels

• Growing interest in CPO (Co-Packaged Optics) technology

However, one thing is clear:

DAC and AOC will continue to coexist and evolve as fundamental interconnect technologies for AI data centers in the foreseeable future.

They will remain critical solutions for building efficient, scalable, and high-performance AI networking infrastructures.

5、Frequently Asked Questions (FAQ)