How to Choose High-Speed Cables for AI Data Centers: DAC, AEC, AOC, Optical Transceivers, and Interconnect Comparison｜Technology Year：2026

As AI servers, GPU clusters, and data center networks continue moving toward 400G, 800G, 1.6T, and higher bandwidths, choosing a high-speed cable can no longer be based only on whether the connector form factor matches.

Common high-speed interconnect solutions in AI data centers include DAC (Direct Attach Copper), AEC (Active Electrical Cable), AOC (Active Optical Cable), and pluggable optical transceivers with optical fiber.

Each solution differs in transmission distance, power consumption, cost, cable weight, bend radius, maintenance, and signal integrity.

The AI-scale Ethernet ecosystem demonstrated at OFC 2026 included technologies from 100G through 1.6T, covering both advanced copper and optical interfaces. This reflects an important trend: future AI data centers are unlikely to become entirely optical. Different distances and applications will continue to use different interconnect technologies.

The real selection question is therefore:

How fast must the link operate, how far must it reach, how much power can it consume, how should it be routed, and how easy must it be to maintain?

What High-Speed Interconnect Options Are Common in AI Data Centers?

High-speed physical interconnects used in AI servers and data centers can generally be divided into four main categories:

There is no single “best” solution.

The appropriate choice depends on the system architecture and actual application requirements.

Modern data center interconnect portfolios also commonly include DAC, AOC, and optical transceivers at the same time, showing that copper and optical technologies are expected to coexist in AI, HPC, and data center environments.

What Is DAC, and Why Is It Common for Short-Reach High-Speed Connections?

DAC, or Direct Attach Copper, is a high-speed cable assembly that integrates high-speed connectors with copper cable.

A passive DAC does not require optical conversion or active signal-processing components.

Its main advantages include:

• Low power consumption
• Low latency
• Simple architecture
• Relatively low cost
• Plug-and-play installation

For very short links inside the same rack or between nearby equipment, DAC is often one of the first solutions to evaluate.

However, as data rates increase, copper channels typically face tighter loss budgets.

This means there is no universal rule that a DAC can always support a fixed distance.

Actual usable cable length depends on:

Data Rate + Lane Rate + Cable Construction + AWG + Connector + Equipment Channel Requirements

What Is AEC, and Why Is It Increasingly Used in AI Data Centers?

AEC, or Active Electrical Cable, still uses copper as the transmission medium.

Unlike passive DAC, however, AEC integrates active signal-processing components such as:

• Retimers
• Gearboxes
• FEC
• Signal conditioning

The purpose is to:

Improve high-speed electrical signal quality and extend copper interconnect reach.

AEC can therefore be viewed as an important option between passive DAC and optical solutions.

As 400G, 800G, and higher-speed architectures become more common, AEC has become an increasingly relevant option for AI clusters and data center interconnects.

What Is AOC?

AOC, or Active Optical Cable, integrates optical transceivers and optical fiber into one complete cable assembly.

Its physical usage is similar to DAC:

Connector → Cable → Connector

However, the signal traveling through the cable is optical rather than high-speed electrical.

Typical advantages include:

• Longer reach than passive DAC
• Lighter and thinner cable
• Better suitability for high-density cable routing
• Strong immunity to electromagnetic interference
• No need to separately purchase optical modules and fiber patch cords

AOC can therefore be attractive when the required distance exceeds what passive copper can comfortably support, while the user still prefers a simple integrated cable assembly.

What Is the Difference Between AOC and Optical Transceivers with Fiber?

This is one of the most common sources of confusion in data center interconnect selection.

Both AOC and pluggable optical solutions use optical fiber, but the architecture is different.

AOC

Integrated Optical Connector + Fiber + Integrated Optical Connector

The complete assembly is manufactured as one cable.

Pluggable Optical Transceiver

Optical Module + Detachable Fiber + Optical Module

The modules and fiber can be replaced independently.

One of the main strengths of pluggable optical transceivers is the ability to select different module and fiber combinations according to transmission distance and network architecture.

How Should DAC, AEC, AOC, and Optical Transceivers Be Selected?

Before considering specific brands or equipment restrictions, the technologies can be compared using the following general logic:

This table is intended only to explain general selection direction.

It is not a fixed specification for every product or data rate.

Actual 400G, 800G, or 1.6T systems must always be evaluated against the official specifications of the switch, NIC, GPU server, connector, cable, and optical transceiver.

Should DAC Be the First Choice Within the Same Rack?

If the transmission distance is very short and passive DAC meets the equipment requirements, DAC is often the first option worth evaluating.

The reason is straightforward:

No additional optical conversion → lower power → simpler architecture → usually lower cost

However, cable management must also be considered when link density increases.

High-speed copper cables can create challenges related to:

• Cable diameter
• Weight
• Bend radius
• Cable routing
• Airflow
• Rack cable density

Distance alone should therefore never determine the final choice.

When Should AEC Be Considered Instead of DAC?

AEC becomes worth evaluating when:

Passive DAC cannot meet the required distance

or when:

A DAC would need to become too thick or heavy to stay within the required loss budget.

Active signal conditioning provides greater flexibility while retaining copper transmission.

However, because AEC contains active electronics, additional factors must be evaluated:

• Power consumption
• Thermal design
• Latency
• Device compatibility
• FEC
• Retimer architecture

AEC should not be treated as a completely equivalent replacement for passive DAC.

When Should AOC Be Selected?

AOC is particularly useful when:

The required distance exceeds practical DAC or AEC reach

while the application still benefits from:

An integrated cable assembly, simple installation, and reduced cable weight.

AOC is commonly used for high-speed switch-to-switch, switch-to-server, and switch-to-GPU connections in data center environments.

If structured fiber cabling and independently replaceable optical modules are not required, AOC can provide a relatively simple optical interconnect solution.

When Should Pluggable Optical Transceivers Be Selected?

Pluggable optical transceivers with fiber are generally more appropriate when the system requires:

• Rack-to-rack connectivity
• Row-to-row connectivity
• Data hall links
• Longer transmission distances
• Structured fiber cabling
• Future equipment upgrades
• Independent module and fiber maintenance

In these situations, the flexibility of:

Pluggable Optical Transceiver + Optical Fiber

becomes a major advantage.

Depending on the transceiver and optical standard, this architecture can support a wide range of transmission distances within and beyond the data center.

Can the Same Selection Rules Be Applied to 400G, 800G, and 1.6T?

The overall selection logic remains similar:

Distance → Power → Cost → Cable Management → Serviceability

However, the actual cable reach and channel limitations cannot simply be reused across different generations.

As signaling rates increase, requirements related to:

• Signal integrity
• Insertion loss
• Connector loss
• Crosstalk
• PCB channel design

generally become more demanding.

Therefore:

If a specific DAC length works in a 400G system, it should not automatically be assumed that the same length will work at 800G or 1.6T.

Every generation should be evaluated using the official specifications of the actual equipment and cable assembly.

A Practical Selection SOP for AI Data Center High-Speed Cables

For engineering, procurement, and NPI projects, the selection process can follow these steps.

Step 1｜Confirm the Interface and Data Rate

Examples include:

QSFP56, QSFP-DD, OSFP, 400G, 800G, 1.6T

Step 2｜Confirm the Actual Distance

Identify whether the connection is:

Server-to-Switch, Switch-to-Switch, or Rack-to-Rack

and determine the true cable routing distance.

Step 3｜Start with the Lowest-Complexity Solution

If passive DAC can meet the requirements:

Evaluate DAC first.

If distance or cable management becomes difficult:

Evaluate AEC.

If the distance increases further:

Evaluate AOC or optical transceivers.

Step 4｜Check Power and Thermal Requirements

Active cables and optical solutions contain active electronic or optical components.

Port power and thermal conditions must therefore be included in system-level evaluation.

Step 5｜Confirm Equipment Compatibility

Do not check only the connector shape.

Also verify:

• Data rate
• Lane configuration
• FEC
• EEPROM / firmware
• Vendor compatibility
• Breakout configuration
• Cable length
• Optical interface

Step 6｜Confirm the Maintenance Strategy

If the system requires easy replacement of optical modules, reuse of fiber infrastructure, or long-term data center expansion, independent optical transceivers usually provide greater flexibility.

High-Speed Cable Selection Cannot Be Based Only on Connector Shape

One of the most common mistakes in AI data center interconnect selection is assuming:

If the connector is the same, the cable must be interchangeable.

In reality, even two products using QSFP-DD or OSFP may differ in:

• Data rate
• Lane rate
• Electrical interface
• Optical interface
• FEC
• Pin assignment
• Cable construction
• Breakout architecture
• Power requirements
• Equipment compatibility

High-speed cable and optical interconnect selection should therefore follow:

Equipment Specification → Interface → Data Rate → Distance → Channel Requirements

rather than starting with connector appearance alone.

The Core Selection Logic for DAC, AEC, AOC, and Optical Transceivers

The entire article can be summarized in one principle:

For the shortest links, evaluate DAC first. As distance increases while copper is still preferred, consider AEC. For longer and lighter integrated optical connections, consider AOC. For longer reach, modularity, and greater maintenance flexibility, evaluate pluggable optical transceivers with fiber.

This is only the first level of selection.

A complete AI data center interconnect decision must also consider:

Speed + Distance + Power + Thermal + Cable Management + Signal Integrity + Compatibility + Serviceability

As AI servers and GPU clusters continue to scale, high-speed interconnects are no longer simply “cables.”

They are part of the infrastructure that directly affects bandwidth density, power consumption, cable routing, serviceability, and overall data center reliability.

Frequently Asked Questions

What Is the Main Difference Between DAC and AOC?

DAC uses copper to transmit high-speed electrical signals and is generally best suited for shorter distances. AOC uses optical fiber and integrates optical conversion at both ends, making it suitable for longer links with lighter cable construction.

What Is the Difference Between AEC and DAC?

Both use copper. DAC is usually passive, while AEC integrates active signal-conditioning technologies such as retimers to improve signal quality and extend electrical reach.

Which Is Better, AOC or Optical Transceivers?

Neither is universally better. AOC provides simple installation because the optical cable assembly is fully integrated. Optical transceivers with detachable fiber provide greater modularity, maintenance flexibility, and structured cabling options.

Will AI Data Centers Eventually Use Only Optical Fiber?

Not necessarily. Copper continues to provide advantages in short-reach applications, including low latency, low power, and relatively low cost. Future data centers are more likely to use a combination of copper and optical technologies according to distance, bandwidth, and system requirements.

Can Any 800G Cable Be Used with Any 800G Device?

Not necessarily. Even when the total bandwidth is 800G, the form factor, lane architecture, FEC, firmware, breakout configuration, cable type, and device compatibility must still be verified.

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Whether you are looking for connectors, cables, wire harness assemblies, electromechanical components, or complete electronic interconnect solutions, SyncTronics provides professional technical support and engineering evaluation for product selection, specification verification, New Product Introduction (NPI), OEM/ODM customization, as well as high-speed transmission, high-reliability, and other specialized application requirements.

We welcome you to visit our Contact Us page and share your project requirements and contact information. Our team is committed to responding quickly and professionally, evaluating the most suitable products and electronic interconnect solutions based on your product specifications, application requirements, and project objectives. We also provide technical recommendations and customized engineering support to help shorten product selection and development time, reduce project risks, and accelerate your path to mass production. We look forward to the opportunity to work with you and provide reliable technical support and practical solutions for every stage of your project.

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