As data center network speeds continue to increase, 400G technology has become one of the core configurations of modern data centers. In practice, it is important to choose the right connection solution.
400G DAC (Direct-Attached Copper) and 400G AOC (Active Optical Cable) are two common solutions. Each of them has its own characteristics and is suitable for different scenarios. This article will explore in detail how to choose between 400G DACs and 400G AOCs in real-world deployments.
What is 400G DAC and 400G AOC？
400G DAC（Direct Attach Cable）
DAC is a copper cable that is directly connected over short distances, and it is the preferred choice for short-distance transmission. It is widely used for short-distance connections between servers and switches. It transmits electrical signals directly via physical cables without the need for photoelectric conversion. Its biggest advantages are low cost, low latency, and low power consumption. But it has a limited transmission distance, usually within 5-7 meters.
400G AOC（Active Optical Cable）
AOC is a fiber-optic active fiber optic cable that uses optical signals to transmit data in an optical fiber and then convert it back into an electrical signal. This enables signal transmission via photoelectric conversion. Its biggest advantages are longer transmission distances (up to more than 100 meters), high immunity to interference, and high flexibility. But the price is relatively high, and the power consumption is slightly higher than that of DACs.
Main Differences Between 400G DAC and 400G AOC
Character | 400G DAC | 400G AOC |
Transmission Medium | Copper | Optical Fiber |
Transmission Distance | 1-7 meters | 7-100 meters or more |
Anti-interference Capability | Susceptible to electromagnetic interference（EMI） | Excellent immunity to electromagnetic interference |
Cost | Low cost | High cost |
Power Consumption | Low power consumption | Slightly Higher power consumption |
Application Scenarios | High-density, short-range interconnects (e.g., ToR Switch to Server, Up to 2.5m) | Medium- to long-distance connections (e.g. EoR Switch to Server, Up to 30m) |
Critical Factors in 400G DAC and 400G AOC selection
- Transmission Distance
DACs are the best choice for applications ranging from 1 to 7 meters, with consistent performance and low cost. For scenarios that require 7-100 meters, AOC is more suitable, and it supports medium and long-distance device interconnection.
- Performance Requirements
Signal integrity: The performance of the DAC is no different from the AOC over short ranges, but the signal attenuation is noticeable beyond 7 meters; AOC maintains high performance over longer distances.
Anti-interference capability: In strong electromagnetic interference environments, AOC is more advantageous.
- Cost Budgeting
DAC is the preferred option for low-cost deployments, especially in data centers with limited budgets.
AOC has a higher initial cost but has a cost-effective advantage over long distances.
- Power Consumption and Heat Dissipation
The low power consumption of the DAC makes it ideal for high-density deployments. AOC consumes slightly more power, but the low heat characteristics of the fiber can help alleviate heat dissipation pressure.
- Device compatibility
Ensure that the DAC and AOC are compatible with common interfaces, such as QSFP-DD or OSFP, and meet the hardware requirements of the network equipment.
Application Scenarios of 400G DAC and 400G AOC
400G DAC
In-rack connections： For example, the short-distance interconnection between the server and the top-level switch (ToR).
Adjacent rack connections： It is suitable for device interconnection scenarios within 5 meters.
Cost-sensitive deployments： Small to medium-sized data centers or short-distance needs with limited budgets.
Due to the low cost of 400G DAC cables and the height limitation of 42U server cabinets, 400G DAC cables are an ideal solution for short-distance transmission within the cabinet.
400G AOC
Cross-rack connections： When the distance exceeds the DAC’s capability range, the AOC is the more reliable option.
Large-scale cloud data centers： The long-range and interference immunity of AOC are ideal for high-performance computing (HPC) clusters.
Complex electromagnetic environment： For example, in industrial-grade data centers, AOC provides more stable performance.
Due to 400G AOC cables using fiber as the transmission medium, they can achieve longer distances and higher bandwidth than 400G DAC cables and can be used to connect individual switches to create larger switch architectures.
Conclusion
In summary, the selection of 400G AOCs and 400G DACs is based on the layout, budget, and performance requirements of the data center. In the data center, the best price/performance can be achieved by deploying a mix of DACs and AOCs. With proper planning and deployment, 400G DACs and AOCs can work together to provide efficient and stable network connectivity for data centers, helping enterprises achieve their high-speed network goals.
When purchasing high-speed cable products, it is also crucial to choose a reliable supplier. MVSLINK is a reliable provider of optical network solutions to build a fully connected, intelligent world through innovative computing and networking solutions.
