With the rapid rise of artificial intelligence, large-scale model training, and high-performance computing (HPC), the demand for higher network bandwidth in data centers is growing at an unprecedented pace. Traditional 400G solutions are gradually reaching their limits, paving the way for 800G interconnect technologies. Among these, DAC (Direct Attach Copper) and AOC (Active Optical Cable) have emerged as mainstream options. Each offers distinct advantages in terms of power consumption, latency, cost, and cabling flexibility.
This article provides an in-depth overview of 800G DAC and AOC cables, exploring their definitions, key features, application scenarios, and typical connection solutions, while also analyzing why they have become essential choices for next-generation data centers.
800G DAC (Direct Attach Copper) is a high-speed interconnection solution based on copper cables, commonly used in QSFP-DD800 or OSFP packaging. It directly transmits electrical signals through passive or active copper wires without the need for photoelectric conversion, offering advantages of extremely low latency and ultra-low power consumption. This solution is cost-effective and highly reliable, making it very suitable for high-speed interconnections within data center racks or between adjacent devices, but with limited cabling flexibility and transmission distance.
Features
Short transmission distance: Generally ≤ 2–3 meters (passive), active DAC (ACC) can extend to about 5–7 meters.
Low latency: Direct transmission of electrical signals with almost no additional latency.
Low cost: Lower price compared to optical modules and fiber solutions, suitable for connections within racks or between adjacent racks.
Low power consumption: Passive DAC consumes basically no power, and active DAC has much lower power consumption than optical modules.
Poor flexibility: Copper cables are thicker, with larger bending radius and heavier weight.
Application Scenarios
Short-distance interconnection between servers and ToR (Top of Rack) switches.
High-speed interconnection within data center racks.
Application environments that are extremely sensitive to latency with limited distance.
800G AOC (Active Optical Cable) is an active fiber optic cable with built-in photoelectric conversion modules, capable of converting electrical signals into optical signals for transmission. It also uses QSFP-DD800 or OSFP packaging, supports PAM4 technology, and achieves bandwidth up to 800Gbps. AOC offers advantages such as light weight, good flexibility, and convenient cabling, with transmission distances reaching 30–100 meters, far exceeding DAC. It is very suitable for inter-rack, medium-short distance interconnections, and GPU cluster connections. Compared to DAC, it has higher power consumption and cost, but it has obvious advantages in flexibility and scalability.
Features
Long transmission distance: Typically 30–100 meters, far exceeding DAC.
Light weight and good flexibility: Fiber optic material, easier to cable than copper cables.
High bandwidth: Single link 800Gbps, supporting large-scale data center interconnections.
Higher power consumption: Compared to DAC, it requires photoelectric conversion at both ends, resulting in significantly increased power consumption.
Medium cost: Higher than DAC, lower than pluggable optical modules.
Application Scenarios
Medium-short distance interconnections between racks and rows (>3 meters, ≤100 meters).
GPU cluster interconnections, large-scale AI training and inference environments.
Data centers with requirements for flexible cabling and lightweight design.
| Feature | 800G DAC (Direct Attach Copper)
|
800G AOC (Active Optical Cable)
|
|---|---|---|
| Transmission Medium | Copper cable | Optical fiber |
| Reach | 0.5 – 3m (passive), up to 5–7m (active/ACC) | 3 – 30m, up to 100m |
| Latency | Ultra-low (direct electrical transmission) | Low (requires electrical-optical conversion) |
| Power Consumption | Near zero (passive), very low (ACC) | Moderate (active components required) |
| Cost | Low | Medium (higher than DAC, lower than pluggable optics) |
| Weight & Flexibility | Heavy, less flexible | Lightweight, highly flexible |
| Typical Use Cases | Intra-rack or adjacent rack connections | Inter-rack, row-to-row, GPU clusters, AI/HPC platforms |
The reasons for choosing 800G DAC and AOC are mainly related to data center development trends, performance requirements, and cost considerations.
In ultra-short distance connections within racks or between adjacent racks, 800G DAC becomes the best choice due to its ultra-low power consumption, extremely low latency, and lower cost. DAC does not require photoelectric conversion; signals are transmitted directly through copper cables with almost no additional latency, making it very suitable for latency-sensitive application scenarios.
Additionally, DAC has a simple structure and high reliability, which helps reduce operational complexity and overall network costs. For large-scale, dense interconnections between servers and switches in data centers, DAC is the most cost-effective solution.
When the interconnection distance exceeds 3 meters, DAC is limited by transmission loss and cable flexibility, making it difficult to meet the requirements. At this time, 800G AOC becomes the ideal choice. AOC has built-in photoelectric conversion modules, with transmission distance extendable to 30–100 meters, and also possesses advantages such as light weight, good flexibility, and easy cabling, which can significantly reduce data center cabling complexity and machine room congestion issues.
For GPU clusters, AI training platforms, and large-scale data centers, AOC provides high-bandwidth, low-latency, and flexible deployment interconnection methods, serving as an important foundation for ensuring the efficient operation of AI and HPC workloads.
800G DAC (Direct Attach Cable) and AOC (Active Optical Cable) are commonly used high-speed interconnect solutions in data centers and high-performance computing environments, primarily designed to support 800Gbps data transmission rates. They differ in transmission medium, distance, and cost, making them suitable for different application scenarios.
800G DAC is mainly used for short-distance interconnections within data centers, such as direct connections between servers and ToR (Top-of-Rack) switches, or high-speed links between devices within the same rack. In typical deployment scenarios, DAC enables point-to-point connections between server NICs and switch ports through QSFP-DD800/OSFP interfaces. Passive DACs are suitable for in-rack applications ranging from 0.5 to 3 meters, while Active DACs (ACC) can extend to 5–7 meters to meet inter-rack connectivity requirements. With advantages of low latency, low power consumption, and low cost, DAC has become the preferred solution for high-density connections inside large-scale data centers.
Connection schemes mainly include point-to-point and breakout configurations, applicable to interconnections among servers, switches, and storage devices.
800G AOC is better suited for mid- to short-distance interconnections between racks or rows, supporting transmission distances of 30–100 meters. It is commonly deployed in GPU clusters, AI training platforms, and hyperscale data centers. In typical scenarios, AOC uses optical fiber channels to connect servers, storage systems, and core switches, enabling flexible cable management and large-scale expansion. Compared with DAC, AOC is lighter in weight and easier to deploy, effectively reducing cable congestion in data centers. As a result, it has become a key interconnect solution for ensuring high bandwidth and low latency in AI clusters and cloud computing environments.
Overall, 800G DAC and AOC complement each other in data centers: DAC, with its advantages of low cost and low latency, is ideal for in-rack or short-distance interconnections, while AOC, with its lightweight design and mid-range transmission capability, plays a key role in GPU clusters and large-scale AI training platforms. By combining these two solutions, data centers can achieve the optimal balance among performance, energy efficiency, and cost. As computing power demands continue to grow, 800G DAC and AOC will remain core interconnect technologies, driving AI and cloud computing infrastructures toward higher bandwidth, lower latency, and greater flexibility.
