From 400G to 1.6T丨AI Data Center Optical Interconnect Solutions

AI infrastructure is moving rapidly from 400G to 800G and toward 1.6T connectivity. As GPU clusters become larger and AI workloads generate more east-west traffic, optical interconnects are becoming a critical part of data center network architecture.

C-LIGHT provides optical transceivers, DAC/AOC cables, and high-speed interconnect solutions designed for AI data centers, supporting network upgrades from 400G to 800G and next-generation 1.6T architectures.

1. Why Optical Interconnects Matter for AI Data Centers

AI training and inference require high-speed communication between GPUs, switches, storage systems, and data center networks.

Workloads such as:

• Large Language Model (LLM) training

• Distributed AI inference

• Mixture of Experts (MoE)

• AllReduce communication

• Model and checkpoint synchronization

can generate massive east-west traffic inside the data center.

As GPU clusters scale, traditional lower-speed connections can become network bottlenecks. Higher-speed optical interconnects help increase bandwidth, reduce network congestion, and support scalable AI cluster architectures.

2. 400G: The Foundation for High-Speed AI Networks

400G optical interconnects are widely used in modern data center and AI network deployments.

Typical 400G solutions include:

• 400G QSFP-DD SR8 for short-distance connections

• 400G QSFP-DD DR4 for data center interconnects

• 400G QSFP-DD FR4 for medium-distance links

• 400G QSFP-DD LR4 for longer-distance transmission

• 400G DAC and AOC for short-range server and switch connections

400G can be deployed between GPU servers, Top-of-Rack (ToR) switches, leaf switches, and spine switches, depending on network architecture and transmission distance.

3. 800G: Scaling AI Network Bandwidth

As AI clusters continue to expand, 800G is becoming an important step in network evolution.

Compared with 400G, an 800G link can provide twice the bandwidth while helping reduce the number of physical connections required for the same aggregate capacity.

Common 800G solutions include:

• 800G OSFP SR8

• 800G OSFP 2DR4

• 800G OSFP 2FR4

• 800G QSFP-DD 2DR4

• 800G QSFP-DD 2FR4

• 800G DAC and 800G AOC

A typical AI data center architecture may use 800G DAC or AOC for short GPU-to-switch connections, while 800G DR8 or 2×FR4 optical transceivers can be used for higher-speed switch-to-switch links.

4. 1.6T: The Next Generation of AI Connectivity

The rapid development of AI accelerators and large-scale GPU clusters is driving the industry toward 1.6T interconnects.

1.6T solutions are expected to support higher-density switch architectures and increasingly demanding AI fabrics.

Potential 1.6T interconnect technologies include:

• 1.6T OSFP-XD optical transceivers

• 1.6T DAC and AEC solutions

• 1.6T optical modules

• Next-generation silicon photonics

• LPO and other low-power optical technologies

At 1.6T, power consumption, thermal management, signal integrity, and port density become increasingly important considerations. Optical interconnect design therefore needs to balance bandwidth, reach, power efficiency, and deployment cost.

5. AI Data Center Optical Interconnect Architecture

A high-speed AI data center can be divided into several connectivity layers:

GPU Layer

GPU servers connect to ToR or leaf switches using high-speed DAC, AOC, or optical transceivers.

Leaf Layer

Leaf switches aggregate traffic from multiple GPU servers and connect to the spine network using 400G or 800G optical interconnects.

Spine Layer

Spine switches provide high-bandwidth connectivity across the AI fabric. 800G and future 1.6T solutions can increase network capacity while supporting higher-density architectures.

Data Center Interconnect

For longer-distance connections between data centers, coherent optical technology, DWDM, and high-speed optical modules can provide scalable bandwidth.

6. C-LIGHT AI Optical Interconnect Solutions

C-LIGHT supports multiple generations of high-speed data center interconnect technologies.

400G Solutions

C-LIGHT 400G portfolio includes:

• 400G SR8

• 400G DR4

• 400G FR4

• 400G LR4

• 400G DAC

• 400G AOC

These solutions can be used for GPU clusters, Ethernet data centers, storage networks, and high-performance computing environments.

800G Solutions

The 800G portfolio includes:

• 800G OSFP SR8

• 800G OSFP DR8

• 800G OSFP 2×FR4

• 800G QSFP-DD800 DR8

• 800G QSFP-DD800 2×FR4

• 800G DAC

• 800G AOC

These products are designed for high-bandwidth AI and data center networks where bandwidth density and low-latency connectivity are important.

1.6T Solutions

For next-generation AI infrastructure, C-LIGHT is also developing solutions around 1.6T architectures, including OSFP-XD-based optical connectivity and high-speed DAC/AEC interconnects.

The goal is to provide a practical upgrade path from 400G and 800G to 1.6T without requiring a complete redesign of the network architecture.

7. Optical Interconnect Selection Guide

The appropriate interconnect depends on transmission distance, network architecture, port density, power budget, and deployment cost.

8. From 400G to 1.6T

The evolution of AI networking can be summarized as:

400G → 800G → 1.6T

400G provides the foundation for high-speed AI networking. 800G increases bandwidth density and becomes increasingly important as GPU clusters scale. 1.6T represents the next stage for large-scale AI fabrics, where bandwidth, power efficiency, thermal performance, and port density must be optimized together.

For data center operators and system integrators, planning an upgrade path early can help avoid network bottlenecks and simplify future expansion.

9. Conclusion

AI data center networking is entering a new high-bandwidth era. From 400G to 800G and eventually 1.6T, optical interconnects will play an increasingly important role in connecting GPUs, switches, storage systems, and data centers.

C-LIGHT provides a scalable portfolio of optical transceivers, DAC, AOC, and next-generation interconnect solutions to support different AI networking architectures and deployment requirements.

Whether building a 400G Ethernet network, upgrading to an 800G AI fabric, or preparing for 1.6T connectivity, choosing the right optical interconnect technology is essential for building a high-performance and scalable data center network.

10.AI Data Center Optical Interconnect Solutions Q&A