800G Modules New Arrival!

800G Modules New Arrival!

800G Modules New Arrival!

400G DAC & 400G AOC: How to Choose?

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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 Direct Attach Cable

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.

400G Active Optical Cable

 

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

  1. 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.

 

  1. 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.

 

  1. 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.

 

  1. 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.

 

  1. 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.

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