English
For a long time, Direct Attach Copper (DAC) cables dominated intra-rack interconnects due to their cost-effectiveness. However, as signal rates soar to 400G, the physical loss and bulky form factor of copper cables have reached their breaking point. At transmission distances exceeding 3 meters, signal integrity challenges make traditional cabling increasingly inadequate.
Against this backdrop, the 400G AOC (Active Optical Cable) has emerged as a frontrunner. By ingeniously combining the high-bandwidth, low-loss properties of optical fiber with the plug-and-play convenience of electrical interfaces, the AOC does more than just solve signal attenuation issues at short distances. Its lightweight design and superior electromagnetic compatibility (EMC) have made it the "Efficiency King" of interconnects within AI computing centers.
What Is 400G AOC Cable?
400G AOC (Active Optical Cable) is a highly integrated optical communication interconnect solution designed for high-speed, short-reach data transmission. At first glance, it appears as a fixed-length fiber cable terminated with 400G transceivers (typically in QSFP-DD or OSFP form factors) at both ends. However, unlike a "passive" copper cable, the AOC is "active" because it contains sophisticated optoelectronic components within its connector heads.
The magic of 400G AOC lies in its internal "Electrical-to-Optical" conversion process:
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Transmitting End: It receives high-speed electrical signals from the switch. A driver chip modulates these signals—typically using 53.125 GBaud PAM4 technology—to power internal VCSEL (Vertical-Cavity Surface-Emitting Laser) arrays.
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Optical Transmission: The data travels through internal Multimode Fiber (MMF) as light pulses, completely bypassing the electromagnetic interference (EMI) and high-frequency attenuation that plague copper cables at 400G speeds.
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Receiving End: At the opposite terminal, a Photodiode array detects the light and converts it back into electrical signals for the host equipment.
This "Electrical-In, Optical-Inside, Electrical-Out" design allows the 400G AOC to offer the same plug-and-play simplicity as a copper cable, while achieving superior signal integrity over distances up to 100 meters. It serves as the ideal bridge in modern data centers, filling the gap where DACs fall short in distance and discrete optical transceivers become overkill in cost.
Application of 400G AOC Cable
In modern network architectures, 400G AOCs are not a "one-size-fits-all" solution, but they offer unparalleled advantages within the "short-to-medium" distance. Their core applications are concentrated in three key areas:
AI Training & HPC Clusters
Large Language Model (LLM) training requires extreme interconnect bandwidth and ultra-low latency between GPUs. 400G AOCs are frequently used to connect high-performance computing nodes (such as NVIDIA H100/B200) to Leaf Switches. In high-density AI racks, the lightweight and EMI-resistant nature of AOCs ensures better airflow and signal stability within crowded cable trays.
Hyperscale Spine-Leaf Architectures
Within massive data centers, 400G AOCs are the go-to choice for Leaf-to-Spine connectivity. Particularly in scenarios where the distance exceeds 3 meters (the limit for DACs) but is under 30 meters, AOCs provide full 400G line-rate forwarding while significantly reducing deployment costs and power consumption compared to discrete transceivers.
Enterprise Core Switching & Storage Networks
For enterprise core networks upgrading from 100G to 400G, AOCs offer "plug-and-play" convenience. They eliminate the need for specialized fiber cleaning and precision alignment, drastically simplifying the workload for IT operations teams managing high-performance storage networks (such as NVMe over Fabrics).
All in all, 400G AOC is the premier solution for achieving the perfect equilibrium between flexible cabling, superior signal performance, and ease of management.
AICPLIGHT 400G AOC Cable Product Portfolio
At AICPLIGHT, we have developed a comprehensive suite of 400G AOC cable solutions optimized for various network topologies. From hyperscale cloud data centers to high-performance AI clusters sensitive to latency and thermals, AICPLIGHT is committed to providing reliable interconnects that meet the most stringent requirements.Our product line extends beyond standard QSFP-DD and OSFP cables to include flexible Breakout solutions, helping users scale bandwidth while optimizing rack space and overall TCO (Total Cost of Ownership).
400G QSFP-DD Ethernet Active Optical Cable
As the mainstream 400G interconnect for modern data centers, this cable features QSFP-DD connectors at both ends, supporting 8 channels of 50G PAM4 modulation. AICPLIGHT's 400G QSFP-DD AOC offers exceptional compatibility and ultra-low Bit Error Rates (BER), making it the most cost-effective choice for switch-to-switch or server-to-switch interconnects within a 30-meter range.
Figure 1: Standard switch-to-switch 400G interconnect utilizing the AICPLIGHT 400G QSFP-DD AOC. This configuration is ideal for spine-leaf architectures requiring high-speed data throughput with minimal latency and simplified cabling.
400G OSFP Flat Top to 400G QSFP-DD Ethernet Active Optical Cable
Designed to bridge the gap between different form factors, this cable features an OSFP Flat Top connector on one end and a standard QSFP-DD on the other. It provides maximum flexibility for users operating in mixed-infrastructure environments, enabling seamless 400G line-rate transmission across heterogeneous hardware.
Figure 2: High-performance AI interconnect scenario utilizing the AICPLIGHT 400G QSFP-DD to OSFP AOC to bridge a 400G Ethernet switch with an NVIDIA H100 GPU server.
400G OSFP Finned Top to 2x 200G QSFP56 Ethernet Active Optical Breakout Cable
Tailored for high-heat density AI computing environments, this breakout cable features an OSFP Finned Top connector with integrated heatsinks for superior thermal management at the switch side. It splits into two 200G QSFP56 connectors, allowing for precise 400G port channelization into dual 200G links, significantly enhancing port density and deployment efficiency.
Figure 3: Typical application of AICPLIGHT 400G OSFP to 2x 200G QSFP56 Breakout cable: Distributing a single 400G switch port into dual 200G links for high-performance server connectivity in InfiniBand or Ethernet environments.
400G QSFP-DD to 2x 200G QSFP56 Ethernet Active Optical Breakout Cable
Specifically engineered for bandwidth distribution within QSFP-DD architectures, this cable transforms a single 400G QSFP-DD port into two 200G QSFP56 links. It serves as the ideal link between high-bandwidth core switches and next-generation Server NICs, ensuring impeccable signal integrity across complex breakout topologies thanks to its lightweight design and active optical performance.
Figure 4: Typical application of AICPLIGHT 400G AOC Breakout cable: Splitting a single 400G port from a Mellanox switch into dual 200G links for high-density server connectivity.
Which AICPLIGHT 400G AOC Cable is Right for You?
To make the best choice within your network topology, use this simple decision logic:
Choose QSFP-DD (Direct Connect): If you are operating in a standard hyperscale Ethernet environment where both switch ends utilize the mainstream QSFP-DD form factor.
Choose OSFP Finned Top: If your deployment involves high-performance AI platforms like NVIDIA Quantum-2 (InfiniBand) or Spectrum-4 (Ethernet), where superior thermal management is critical for stability under heavy workloads.
Choose OSFP Flat Top: For devices with strict module height constraints (e.g., specific high-performance NICs) or switches that feature integrated internal heatsinks.
Choose Breakout Cables: When you need to "split" a single 400G port from a core switch to two 200G nodes (such as server NICs) to maximize port density and minimize per-port cost.
Conclusion
As the era of AI and hyperscale data centers transitions to 400G, selecting the right interconnect medium is pivotal for performance and cost-efficiency. AICPLIGHT's 400G AOC portfolio, with its optimized OSFP and QSFP-DD form factors, provides a robust bridge for modern computing clusters. Whether you require the superior thermals of OSFP Finned Top or the versatility of QSFP-DD Breakouts, AICPLIGHT ensures your data travels with peak integrity.
