How to Choose the Right DAC 400Gb/s Cable for Data Center Networks

As data center networks advance toward 400G connectivity, high-speed interconnection has become increasingly important for switches, servers, storage systems, cloud infrastructure, and high-performance computing. However, not every network device needs a native 400G port.

In mixed-speed environments, one 400G switch port may need to connect with multiple 200G, 100G, 50G, or 25G interfaces. A breakout direct attach copper cable can provide a practical solution by distributing one 400G connection across several lower-speed links.

The DAC 400Gb/s cable from Infinol Technology is designed for short-distance, high-bandwidth networking. Its product range includes direct 400G-to-400G connections as well as breakout configurations for 2×200G, 4×100G, 8×50G, and 8×25G applications.

What Is a 400G DAC Breakout Cable?

A standard 400G DAC connects two compatible 400G ports. This is suitable when both switches or network devices support native 400G interfaces.

A breakout DAC uses one 400G connector on one side and multiple lower-speed connectors on the other. This allows a high-speed switch port to communicate with several devices operating at different speeds.

Typical configurations include:

• 400G to 400G

• 400G to 2×200G

• 400G to 4×100G

• 400G to 8×50G

• 400G to 8×25G

The cable configuration must match the capabilities of the connected equipment. The switch, NIC, server, and network adapter must support the required breakout mode and lane mapping.

When Should You Use 400G to 2×200G?

A 400G-to-2×200G DAC is useful when one 400G port needs to connect with two 200G interfaces.

This configuration can support network upgrades in which the aggregation layer moves to 400G while downstream equipment remains at 200G. Instead of replacing every 200G endpoint, a compatible 400G port can provide two 200G connections.

Infinol offers OSFP-to-2×200G and QSFP-DD-to-2×200G configurations. The breakout side uses QSFP56 interfaces, making these cables suitable for compatible 200G equipment.

The OSFP400G-2Q200G-CU and QDD400G-2Q200G-CU series are available in short cable lengths for rack-level connections.

400G to 4×100G for Data Center Networks

A 400G-to-4×100G breakout cable divides one 400G interface into four 100G links.

This architecture is useful when a 400G aggregation switch needs to connect with multiple 100G servers, switches, or network interfaces. It can reduce the number of high-speed ports required while allowing existing 100G equipment to remain in service.

Infinol's OSFP400G-4Q100G-CU and QDD400G-4Q100G-CU families provide corresponding OSFP and QSFP-DD options.

For data centers upgrading their switching infrastructure, this type of breakout can provide a convenient transition between 100G and 400G networking.

400G to 8×50G Applications

Some networks contain a large number of 50G interfaces. In these environments, an 8×50G breakout can connect one 400G port with eight 50G endpoints.

Infinol provides OSFP-to-8×50G and QSFP-DD-to-8×50G configurations. Depending on the model, SFP or SFP56 interfaces are used on the breakout side.

The OSFP400G-8S50G-CU and QDD400G-8S50G-CU series are designed for short-distance Twinax copper connections.

This configuration can be useful for data centers that want to introduce 400G aggregation without immediately replacing existing 50G equipment.

Why Choose 400G to 8×25G?

25G Ethernet remains widely used for server access and data center connectivity. When aggregation switches are upgraded to 400G, an 8×25G breakout can help maintain compatibility with existing 25G endpoints.

One 400G interface can potentially serve eight 25G ports when the network equipment supports the required breakout configuration.

Infinol offers OSFP-to-8×25G and QSFP-DD-to-8×25G versions using SFP28 interfaces on the breakout side. Available cable lengths include short options suitable for rack-level deployment.

This makes 8×25G particularly useful for phased network upgrades where the aggregation layer and server layer operate at different speeds.

Comparing 400G DAC Configurations

There is no universal best configuration. The correct choice depends on the port speeds and connector types already installed in the network.

OSFP or QSFP-DD for 400G?

The connector on the 400G side must be checked before ordering.

Infinol provides both OSFP and QSFP-DD 400G DAC solutions. For OSFP-based equipment, the OSFP-400G-CU family supports direct 400G connections, while OSFP breakout models provide different lower-speed configurations.

For QSFP-DD equipment, the QSFP-DD-400G-CU family supports direct 400G connectivity. QDD400G breakout products cover configurations including 2×200G, 4×100G, 8×50G, and 8×25G.

Although OSFP and QSFP-DD are both used in high-speed networking, their physical interfaces are different. The exact switch model and port type should therefore be confirmed before selecting a cable.

Why Use Twinax Copper for Short 400G Links?

Direct attach copper is well suited to short connections inside racks or between closely positioned network devices.

Infinol's 400G DAC products use Twinax copper and are designed for approximately 1 to 3 meters of reach, with selected QSFP-DD models also available in 2.5-meter versions.

For short-distance connections, DAC can simplify installation because the interfaces are integrated into the cable assembly. This avoids the need for separate optical modules and fiber patch cables when copper transmission meets the system requirements.

Cable length should also be selected according to the physical layout. A 1-meter cable may be suitable for adjacent equipment, while 2-meter or 3-meter versions can provide greater routing flexibility. Excess cable should be avoided in high-density racks because it can complicate cable management and airflow.

Power Efficiency at 400G

Power consumption becomes increasingly relevant as the number of high-speed ports grows.

The 400G DAC platform from Infinol features low power dissipation and uses a single 3.3V power supply. In large data centers, the power characteristics of individual interconnects can contribute to overall rack-level energy requirements.

However, engineers should evaluate the complete network link rather than the cable alone, including switch ports, adapters, cooling, and other active components.

For short links where copper DAC is technically appropriate, its low-power characteristics can support efficient high-density network deployment.

What to Check Before Buying a 400G DAC

Before selecting a 400G DAC or breakout cable, confirm the following:

400G port type: Check whether the equipment uses OSFP or QSFP-DD.

Breakout configuration: Determine whether the requirement is 400G-to-400G, 2×200G, 4×100G, 8×50G, or 8×25G.

Downstream connector: Confirm whether the lower-speed equipment uses QSFP56, QSFP, SFP/SFP56, or SFP28.

Switch compatibility: Make sure the switch supports the selected breakout mode and lane mapping.

Cable length: Select a length that provides sufficient routing without unnecessary slack.

Protocol: Verify compatibility with the intended Ethernet or InfiniBand application.

Operating conditions: Check temperature, compliance, and installation requirements.

These checks can prevent integration problems caused by selecting a cable based only on its advertised bandwidth.

About Infinol Technology (Shenzhen) Co., Ltd

Infinol Technology (Shenzhen) Co., Ltd specializes in optical communication products and high-speed network interconnection solutions.

Its portfolio covers optical transceivers and interconnection products supporting multiple generations of network technology, including 25G, 100G, 200G, 400G, and 800G. The company also provides DAC, AOC, MPO/MTP trunk cables, and other active and passive optical communication products.

Its solutions serve data centers, cloud storage, telecommunications, Ethernet, Fibre Channel, InfiniBand, OTN, CPRI, PON, and high-performance computing applications. OEM and ODM services are also available for customers requiring customized optical and interconnection products.

For 400G networking, the company provides both direct-connect DACs and breakout configurations, allowing customers to select a cable according to their actual network topology instead of relying on a single 400G connection type.

Selecting the Right 400G Breakout Solution

The correct 400G DAC depends on the complete connection architecture.

For two native 400G ports, a straight 400G-to-400G cable is appropriate. When a 400G switch needs to connect to two 200G interfaces, a 2×200G breakout can provide the required connection. For four 100G endpoints, a 4×100G configuration may be more suitable. Networks with larger numbers of 50G or 25G devices can consider 8×50G or 8×25G options.

The DAC 400Gb/s cable portfolio from Infinol combines 400G connectivity, OSFP and QSFP-DD options, Twinax copper construction, short-distance reach, and multiple breakout architectures.

By confirming the 400G connector, downstream interface, breakout ratio, cable length, network protocol, and equipment compatibility before purchasing, network engineers can build a practical high-speed interconnection system while maintaining compatibility with existing infrastructure.