The rapid growth of Artificial Intelligence (AI), Large Language Models (LLMs), and high-performance computing (HPC) has dramatically increased the demand for high-speed networking inside modern data centers.
Today's AI clusters may contain hundreds or even thousands of GPUs connected through high-bandwidth Ethernet or InfiniBand fabrics. While GPUs provide the computing power, network interconnects determine how efficiently those GPUs can communicate.
Choosing the right connectivity technology is therefore critical.
The three most common options are:
Direct Attach Cables (DAC)
Active Optical Cables (AOC)
Optical Transceivers
Each solution offers unique advantages depending on distance, deployment architecture, budget, and operational requirements.
Unlike traditional enterprise networks, AI workloads generate enormous east-west traffic.
Examples include:
Distributed AI training
AllReduce communication
Expert routing in MoE models
Parameter synchronization
Storage checkpoint transfers
GPU-to-GPU communication
In these environments, network performance directly impacts:
GPU utilization
Training completion time
Cluster scalability
Energy efficiency
Overall infrastructure ROI
Even a small increase in latency or packet loss can affect thousands of GPUs simultaneously.
This is why selecting the right interconnect solution has become a strategic decision for AI infrastructure operators.
DAC is a copper-based solution with high-speed connectors permanently attached at both ends.
Lowest purchase cost
Lowest power consumption
Extremely low latency
No optical conversion required
Easy deployment
Limited transmission distance
Heavier cable bundles
Difficult cable management in large deployments
0.5m to 5m
GPU server to ToR switch
In-rack GPU connectivity
Switch-to-switch connections within the same rack
For these scenarios, C-LIGHT provides:
These products deliver excellent power efficiency and cost savings for high-density AI racks.
AOC integrates optical transceivers and fiber into a single cable assembly.
It combines the simplicity of DAC with the transmission advantages of fiber optics.
Longer transmission distances
Lightweight cable management
Reduced airflow obstruction
Strong EMI immunity
Simple plug-and-play deployment
Higher cost than DAC
Entire cable must be replaced if damaged
5m to 100m
Cross-rack GPU clusters
Leaf-to-Leaf connections
High-density AI server rooms
C-LIGHT's AOC portfolio includes:
These solutions are widely used in AI fabrics where reducing cable weight and improving airflow are critical.
Optical transceivers provide the highest level of flexibility and scalability.
Unlike AOCs, optical modules and fiber jumpers are separate components, making maintenance easier and supporting structured cabling architectures.
Long transmission distances
Flexible deployment
Easy replacement and maintenance
Supports structured cabling
Ideal for large-scale AI fabrics
Higher upfront investment
Higher power consumption than DAC
100m to 80km+
Leaf-Spine networks
Data Center Interconnect (DCI)
Multi-building AI campuses
Long-distance GPU cluster expansion
C-LIGHT offers a complete optical networking portfolio including:
These products enable scalable AI networking across data halls, campuses, and metropolitan regions.
| Feature | DAC | AOC | Optical Modules |
|---|---|---|---|
| Cost | Lowest | Medium | Highest |
| Power Consumption | Lowest | Medium | Medium-High |
| Latency | Lowest | Very Low | Very Low |
| Cable Weight | Heavy | Lightweight | Fiber-Based |
| Maintenance | Replace Entire Cable | Replace Entire Cable | Replace Module Individually |
| Scalability | Limited | Moderate | Excellent |
| Structured Cabling | No | No | Yes |
| Distance | 0.5-5m | 5-100m | 100m-80km+ |
| AI Deployment Scale | Rack-Level | Cluster-Level | Data Center-Level |
Most AI operators do not rely on a single technology.
Instead, they deploy a combination of all three.
Use DAC.
The short distance makes DAC the most economical and energy-efficient option.
Use AOC.
The lightweight design simplifies deployment while supporting longer distances.
Use Optical Transceivers.
They provide the flexibility, maintainability, and scalability required for large AI infrastructures.
A common deployment strategy looks like this:
GPU Server → ToR Switch → DAC
ToR Switch → Leaf Switch → AOC
Leaf Switch → Spine Switch → Optical Modules
Building-to-Building → DWDM Solutions
This hybrid approach balances performance, cost, and operational efficiency.
Modern AI platforms powered by NVIDIA H100, H200, and Blackwell GPUs are accelerating the transition to 400G and 800G networking.
As AI models continue to scale, network requirements include:
Higher bandwidth
Lower latency
Better congestion control
Greater energy efficiency
C-LIGHT addresses these requirements with a comprehensive AI networking portfolio covering:
400G DAC
400G AOC
400G DR4
400G FR4
400G LR4
800G DAC
800G AOC
800G DR8
800G 2×FR4
These products are designed to support Ethernet and InfiniBand AI fabrics while enabling future migration toward 1.6T networking.
There is no single "best" interconnect solution for AI clusters.
The optimal choice depends on distance, architecture, scalability requirements, and operational objectives.
A simple rule of thumb is:
Choose DAC for short-distance, cost-sensitive deployments.
Choose AOC for medium-distance, high-density AI networking.
Choose optical transceivers when scalability, structured cabling, and long-distance connectivity are required.
In practice, the most successful AI data centers combine all three technologies to create a balanced, high-performance network architecture.
With a complete portfolio of DAC cables, AOC solutions, optical transceivers, and WDM platforms, C-LIGHT helps customers build reliable, scalable, and future-ready AI networking infrastructures.
