AOC Cable Selection Guide: AOC vs. DAC, Specifications and Buying Considerations

Active Optical Cables (AOCs) combine optical fiber and active optical components into a factory-terminated cable assembly. They provide an integrated way to connect compatible high-speed network equipment while reducing some of the cable bulk and electromagnetic constraints associated with copper-based connections.

As data-center architectures move from 400G and 800G toward higher-speed interconnects, selecting an AOC requires more than matching a headline data rate. Interface type, link architecture, breakout configuration, reach, power consumption, operating environment and system compatibility all need to be considered together.

This guide explains how AOCs work, how they compare with DACs and modular optical-transceiver solutions, and what engineers and B2B procurement teams should check when selecting an AOC.

What Is an AOC Cable?

An Active Optical Cable (AOC) is a factory-terminated fiber-optic cable assembly with active optical components integrated into both ends.

The active components convert electrical signals into optical signals at the transmitting end and convert the received optical signals back into electrical signals at the receiving end. Because these active components are integrated into the cable ends, an AOC requires electrical power from the connected host equipment.

Unlike a conventional passive fiber cable used with separate optical transceivers, an AOC combines the optical transmission path and active conversion functions into one assembled link. This integrated architecture can simplify installation and reduce the number of separately managed components.

For an overview of AOC fundamentals, see T&S's AOCtechnology guide.

How Does an AOC Cable Work?

An AOC performs electrical-to-optical and optical-to-electrical conversion within the cable assembly.

The basic signal path is:

Electrical Signal → E/O Conversion → Optical Fiber → O/E Conversion → Electrical Signal

At the transmitting end, active electronics and optical components convert the electrical input into an optical signal. The signal travels through the fiber to the opposite end, where it is converted back into an electrical signal for the receiving equipment.

Because the conversion components are integrated into both ends of the cable, an AOC is supplied as a complete connection rather than as separate transceivers and fiber patch cables.

This architecture can simplify deployment, but it also means that the cable assembly should be specified around the exact interfaces and requirements of the connected equipment.

Why Are AOC Cables Used in Data Centers?

AOCs are used in data centers and other high-speed network environments where optical transmission, cable density and integrated connectivity are important considerations.

Compared with copper-based direct-attach cables, optical AOCs can provide several practical advantages:

• High-speed optical transmission: Suitable for a wide range of high-speed interconnects, including 400G and 800G applications.

• Lower cable bulk: Fiber-based construction can reduce cable size and weight compared with equivalent high-speed copper assemblies.

• Lower susceptibility to EMI: Optical transmission is inherently less susceptible to electromagnetic interference than electrical transmission over copper.

• High-density deployment: Smaller and lighter cable assemblies can help simplify cable management in dense equipment environments.

• Integrated connectivity: Active optical components and the fiber path are supplied as one factory-terminated assembly.

These characteristics make AOCs suitable for direct connections between servers, switches, accelerators and other compatible network equipment.

AOC should not, however, be treated as a universal replacement for DAC or modular optical-transceiver solutions. The appropriate architecture depends on the specific link requirements.

AOC Cable vs. DAC Cable: What Is the Difference? 

AOC and DAC are both direct-attach cable assemblies, but they use different transmission technologies. AOC uses optical fiber with active optical conversion, while DAC carries electrical signals directly over copper conductors.

The choice between AOC and DAC should be based on the complete link requirement rather than cable price alone. Data rate, reach, cable density, power consumption, equipment interfaces and long-term network architecture can all affect the appropriate choice.

AOC Cable vs. Optical Transceiver + Cable: Which Architecture Fits Better?

An AOC is an integrated optical cable assembly, while a conventional optical architecture uses separate optical transceivers and fiber-optic patch cords.

The main trade-off is therefore integration versus flexibility.

An AOC can simplify installation and reduce the number of separately managed components. A modular transceiver architecture provides greater flexibility when link length, connector type, transceiver generation or cabling configuration may change over time.

How Should You Choose an AOC Cable Specification?

AOC selection should start with the complete link architecture rather than with cable speed alone.

1. Confirm the Required Data Rate

First identify the required network speed, such as 10G, 25G, 100G, 200G, 400G or 800G.

Higher-speed links can involve different electrical lane architectures and host interfaces, so a cable should not be selected solely by its nominal bandwidth.

T&S currently offers AOC solutions covering 10G through 1.6T across multiple product generations and interface configurations.

2. Confirm the Host Interface and Form Factor

The connector or module form factor at each end must match the equipment ports.

Depending on the data rate and application, AOC configurations may include:

SFP+ · SFP28 · SFP-DD · QSFP+ · QSFP28 · QSFP56 · QSFP-DD · QSFP112 · QSFP56-DD · OSFP · OSFP112 · OSFP-DD

Form factor alone does not guarantee system compatibility. The host platform, electrical interface, protocol, module requirements and applicable industry standards should also be checked.

3. Check Straight or Breakout Configuration

Not every high-speed link is a one-to-one connection.

For example, an 800G AOC may be required in configurations such as:

• 800G to 2×400G

• 800G to 4×200G

The correct configuration depends on the architecture of the switch, server, accelerator or other equipment at each end.

For high-density AI and data-center networks, breakout configuration can be as important as the nominal data rate when determining the appropriate AOC.

4. Confirm Reach and Fiber Requirements

AOC reach depends on the specific optical design, data rate, fiber construction and applicable standard.

Cable length should therefore be specified together with the required transmission distance rather than treated as an independent parameter.

For example, T&S's industrial-grade 25G SFP28 AOC supports a maximum length of 70 m over OM3 fiber under its specified operating conditions. This figure applies to that specific product and should not be generalized to all AOCs.

5. Consider Power and Thermal Requirements

Power consumption becomes an increasingly important consideration as data rates increase.

For 400G and 800G applications, buyers should check the specified power consumption of the complete AOC and consider the thermal environment of the host equipment.

A cable that meets the required data rate may still be unsuitable if its power or thermal characteristics do not fit the system design.

6. Check the Operating Environment

Commercial and industrial applications may require different temperature specifications.

For example, T&S's industrial-grade 25G SFP28 AOC is specified for operation from −40°C to +85°C, while other AOC products may use commercial operating-temperature ranges.

Operating temperature, humidity, installation environment and mechanical requirements should therefore be confirmed before final product selection.

7. Verify System Compatibility

This is particularly important for high-speed AOCs.

The procurement specification should identify:

• Host equipment and port type

• Required data rate

• Interface at each end

• Straight or breakout configuration

• Cable length

• Operating temperature

• Protocol or application

• Compatibility requirements

For 400G and 800G deployments, buyers should also verify the applicable electrical lane architecture, FEC requirements and module or MSA compatibility where relevant.

How Do Data Rate and Form Factor Affect AOC Selection?

Data rate and form factor determine the basic physical and electrical compatibility of an AOC, but they do not define the complete link specification.

T&S currently offers AOC products from 10G to 1.6T, covering multiple generations of SFP, QSFP and OSFP interfaces.

For example, a 40G QSFP+ AOC, a 100G QSFP28 AOC and an 800G OSFP AOC are all optical direct-attach assemblies, but they are designed around very different host interfaces, lane architectures and network requirements.

Newer 400G and 800G deployments may also use interfaces such as QSFP112, OSFP112, QSFP-DD and OSFP-DD, depending on the system architecture.

This means the equipment interface should be confirmed before finalizing cable speed, configuration or quantity.

When Is AOC the Right Choice for a Network Project?

An AOC can be a suitable choice when an integrated optical link matches the interfaces and requirements of the connected equipment.

It is particularly useful when a project requires:

• High-speed optical connectivity

• Compact and lightweight cabling

• Direct equipment-to-equipment connections

• Factory-terminated plug-and-play installation

• Standardized cable configurations

• Reduced dependence on separate transceiver and patch-cable components

AOC is generally most appropriate when the link configuration is well defined and component-level flexibility is not the primary requirement.

Where network designers need interchangeable transceivers, different fiber assemblies or future flexibility in link configuration, a modular optical-transceiver architecture may be more appropriate.

AOC Selection for 400G, 800G and Emerging Higher-Speed Networks

As data-center and AI infrastructure move toward higher-speed connectivity, AOC selection is becoming increasingly dependent on the overall interconnect architecture.

At 400G and 800G, buyers may need to consider not only the nominal data rate but also:

Interface generation / Electrical lane architecture / Breakout configuration / Power consumption / Thermal constraints / Reach / Host compatibility

Looking ahead to 1.6T-class architectures, these considerations are expected to become increasingly important as system designers balance bandwidth density, power and cabling complexity.

For this reason, an AOC should be specified as part of the network architecture rather than selected as a standalone cable based only on bandwidth.

Frequently Asked Questions

1. What is an AOC cable used for?

An AOC cable is used for integrated optical connections between compatible high-speed network devices, including switches, servers, accelerators and other data-center equipment.

2. Does an AOC cable contain optical transceivers?

An AOC contains active optical components at both ends that perform electrical-to-optical and optical-to-electrical signal conversion. The exact internal architecture depends on the product design.

3. What is the difference between AOC and DAC?

AOC uses optical fiber and active optical conversion, while DAC uses copper conductors for direct electrical transmission. AOC can provide advantages in high-density, high-speed optical interconnection, while DAC remains suitable for certain short copper links.

4. Is AOC the same as using separate optical transceivers?

No. An AOC integrates the active optical components and fiber into one factory-terminated assembly. A modular optical-transceiver solution uses removable transceivers together with separate fiber cables.

5. What AOC speeds does T&S currently offer?

T&S currently offers AOC product categories covering 10G, 25G, 40G, 50G, 56G, 80G, 100G, 200G, 400G, 800G and 1.6T.

6. Can AOC be used for 400G and 800G connections?

Yes. AOCs are available for 400G and 800G direct high-speed connections, with different host interfaces and breakout configurations depending on the network architecture.

7. What is the maximum distance of an AOC?

There is no single maximum distance for all AOCs. Reach depends on data rate, optical design, fiber type and the applicable product specification. The specified reach of the exact AOC model should always be checked before procurement.

8. What information should be provided when requesting an AOC quotation?

A typical RFQ should include the required data rate, interface at each end, straight or breakout configuration, cable length, operating environment, application or protocol, quantity and any host-equipment compatibility requirements.

Conclusion

Choosing an AOC cable requires more than matching a bandwidth number.

The appropriate configuration depends on the complete link architecture, including data rate, host interface, breakout configuration, reach, power, operating environment and system compatibility.

For high-speed data-center and AI infrastructure, these factors become increasingly important as networks move from 400G and 800G toward higher-density interconnect architectures.

T&S provides AOC solutions up to 1.6T across multiple interface generations and configurations, enabling customers to select integrated optical connectivity around the requirements of their specific network architecture.

References / External Resources

1. The Fiber Optic Association – Fiber Optics for Data Centers
   https://www.foa.org/tech/ref/appln/datacenters.html

2. Cisco – Physical Infrastructure for the Converged Plantwide Ethernet Architecture
   https://www.cisco.com/c/en/us/td/docs/sanity/suman/CPwE-Physical-Infrastructure_Feb2023.html

3. Wikipedia – Fiber-Optic Communication
   https://en.wikipedia.org/wiki/Fiber-optic_communication