The demand for high-speed data communication continues to grow rapidly as data centers and enterprise networks scale. QSFP28 Active Optical Cables (AOCs) have become a popular choice for high-performance interconnects, offering an excellent combination of bandwidth, reach, and deployment simplicity.
This guide covers what AOC cables are, how they work, their advantages over copper solutions, how they compare with DAC cables, and practical selection recommendations.
Need help choosing cables? Explore Ascent Optics’ QSFP28 connectivity solutions or contact our engineers for a free cable assessment.
Active Optical Cables (AOCs) are also data communication type cables made of optical fibers. Unlike copper cables, AOCs are built with Optical Fiber technology which has greater bandwidth, a longer reach, and is lighter and more flexible too. It is composed of electrical mechanical to optical conversion inserts that are affixed within the plugs on both ends, which enable the transmission of electricity to be converted into an optical signal and back to electrical, which makes it possible to communicate between network equipment quickly and efficiently with minimal devices.
Active optical cables integrate advanced technology which transforms electrical to optical signals and vice versa. It leverages the use of Photodiodes and Vertical Cavity Surface Emitting Laser (VCSEL) in the connector modules for conversion. A major benefit of AOC technology allowing transferring of more than 100 Gbps which is essential in modern day data transferring centers.
An AOC consists of several plastic or glass optical fibers surrounded by a relatively strong and light-weight cable jacket. Signals in the optical fibers allow for long-distance transfer of up to several hundred meters without the use of signal boosters. In addition, AOCs require less energy than copper cables, have low latency and minimal EMI thus making them appropriate in energy efficient data centers.
It is not uncommon to find AOCs like the 100G QSFP28 using designs that are increasingly integrated and compact for those in high-performance computer environments or cloud services. These companies require fast and accurate data transfers. As the demand for more bandwidth increases, further developments, such as PAM4 techniques and silicon photonics integration into AOC technology, are likely making promises for greater data throughput in future networks.
The processes performed at the cable end that incorporate the active transmission of data through optical fibers in active optical cables commence by converting the electrical signals. This operation is done by using vertical cavity surface emitting lasers (VCSELs) which emit light for the purpose of sending it through the fiber after receiving an electric signal. These optical signals get encoded back to electrical form by photodiodes when they reach the destination through the connection module. This type of dual conversion allows AOCs to transmit data at very high speeds whilst keeping the signal loss over long distances to a minimum and also helps in the lessening of latency and electromagnetic interference issues. This is very important for the efficient transfer of data in the current network structures.
A comparison of technical parameters reveals the strengths of Active Optical Cables (AOCs) when pitted against conventional alternatives such as copper cables. Here is a detailed comparison:
Data Transmission Rate:
Transmission Distance:
Electromagnetic Interference (EMI):
Cable Weight and Flexibility:
Power Consumption:
Cost Efficiency:
The copper cable, by contrast, is suitable in terms of price for short-range networking solutions while AOC’s are therefore best suited for long-range high-speed applications in current data centers.
AOC vs Copper Cables: Head-to-Head Comparison
| Parameter | Active Optical Cable (AOC) | Copper Cable (DAC) |
| Data Rate | 40G–400G+ | Best for ≤100G (short distance) |
| Maximum Reach | 100–300 meters | Typically 1–7 meters |
| EMI Immunity | Excellent (immune) | Susceptible |
| Weight & Flexibility | Lightweight and highly flexible | Heavier and stiffer |
| Power Consumption | Moderate | Very low |
| Best Use Case | Medium to long reach | Ultra-short reach |
For a broader view of 100G connectivity options, see our QSFP28 transceiver guide.
As data centers continue migrating toward 100G and higher-speed networks, traditional copper cabling increasingly faces limitations in transmission distance, cable bulk, and signal integrity. QSFP28 AOC (Active Optical Cable) has therefore become one of the most widely adopted solutions for high-speed interconnects in modern data centers. By integrating optical transceivers and fiber cabling into a single assembly, AOCs provide an excellent balance of performance, flexibility, and deployment efficiency, especially in high-density networking environments.
Supports stable 100G transmission (4×25G) with excellent signal integrity, making it ideal for cloud computing, AI workloads, and large-scale data exchange.
Compared with DAC cables, AOCs can easily support 30m, 50m, or even 100m+ connections without requiring additional repeaters or signal conditioning.
Fiber-based transmission is completely immune to electromagnetic interference (EMI/RFI), making AOCs highly suitable for complex and high-density data center environments.
AOCs are thinner and lighter than copper cables, simplifying cable routing, improving airflow management, and increasing rack space efficiency.
Built-in active optical conversion enables stable low-latency communication without external amplification.
Fully compatible with mainstream QSFP28 switches, servers, and NICs, enabling simple deployment and cost-effective upgrades.
Compared with copper cabling solutions at similar distances, QSFP28 AOCs typically provide lower link loss, better thermal performance, and simplified cable management. They are particularly well suited for Spine-Leaf architectures, HPC clusters, AI infrastructure, and other large-scale high-speed networking environments where performance, power efficiency, and deployment flexibility are equally important.
In 100G data center networking, both QSFP28 AOC (Active Optical Cable) and DAC (Direct Attach Copper) are widely used interconnect solutions. While both support plug-and-play deployment, they differ significantly in transmission distance, cost, power consumption, and cabling flexibility. The best choice depends on the specific deployment scenario.
DAC is a passive twinax copper cable solution with a simple structure that does not require optical conversion. As a result, it offers low cost, extremely low power consumption, and minimal latency.
DAC is especially suitable for short-range connections within the same rack or between adjacent racks, typically within 5–7 meters. For large-scale deployments, DAC can significantly reduce overall cabling costs while minimizing power usage, making it a preferred option for short-distance Top-of-Rack (ToR) connectivity.
Compared with DAC, AOC uses active optical transmission to provide longer reach and more stable high-speed connectivity, making it more suitable for medium-distance data center interconnects.
AOC is recommended for scenarios such as:
AOCs also help improve airflow and cable management while maintaining relatively low power consumption.
DAC remains the more economical solution for ultra-short-distance connections where minimizing cost and power consumption is the top priority.
DAC is typically recommended for:
In general, DAC is ideal for “short-distance, low-cost, low-power” deployments, while AOC is better suited for “longer-distance, flexible, and stable” high-speed interconnect applications.
To fully leverage the performance and reliability of QSFP28 AOC in data center environments, it is important to pay attention to compatibility, cabling design, and environmental conditions during deployment. Proper planning can improve network stability while reducing maintenance and troubleshooting complexity.
Different AOC models are designed for different distance and application requirements. Select the correct multimode or single-mode AOC solution to ensure optimal performance and cost efficiency.
Before deployment, confirm that switches, NICs, and platforms support the target AOC, including EEPROM recognition, DDM monitoring, and firmware compatibility, to avoid link detection or warning issues.
In Spine-Leaf architectures, AI clusters, or GPU deployments, Breakout AOCs (such as 100G to 4×25G) can improve port utilization while simplifying cable management and reducing rack congestion.
Although AOCs are lighter and more flexible than copper cables, excessive bending can still increase optical loss and impact long-term reliability. Follow the manufacturer’s bend radius recommendations during installation.
In high-density switch or HPC environments, proper airflow and thermal design are critical to maintaining stable operation and extending module lifespan.
In modern data centers, QSFP28 AOCs are widely used for ToR-to-server connections, Leaf-to-Spine interconnects, and GPU cluster networking. Proper planning of cable length, routing paths, and port density can significantly improve deployment efficiency, airflow optimization, and long-term maintenance experience.
QSFP28 AOC cables provide an outstanding balance of performance, reach, and ease of use. They serve as a reliable solution for data centers looking to upgrade bandwidth while maintaining manageable cabling infrastructure.
Understanding when to use AOC versus DAC allows network engineers to optimize cost, performance, and scalability effectively.
Ready to deploy QSFP28 AOCs? Explore Ascent Optics’ complete range of QSFP28, QSFP56, and QSFP-DD Active Optical Cables or contact our team for expert compatibility advice and recommendations.
A: The high performance, speed, and distance of the AOC cables are far superior to those of the copper cables. They apply electrical to optical conversion, which assists in increasing data rates to satisfy the requirements of high-performance computing and data centers.
A: Long distances between devices can be bridged with high-speed transmission without losing the compatibility of standard network devices. They are suited for multi-lane datacom and interconnect applications.
A: What sets AOC and DAC cables apart to some extent is that, unlike DAC cables, which are basic electricity-based cables, AOCs employ electrical-to-optical conversion, which enhances the speed and distance performance of the cable.
A: Certainly, AOC cables are optimal for high-performance computing and are also perfect for long-distance applications needing fast data interconnects that are reliable and have high data rates.
A: Yes, AOC cables utilize a standard QSFP port, allowing users to improve the speed and distance of their networks without any changes to the existing system.
A: Due to the high data rates required for long-distance applications, AOC cables are deployed in data centers, HPC, and telecommunication infrastructures. They are also used in breakout cable systems for multiple outputs from single sources.
A: An AOC cable replaces the metallic transmission media with an optical communication medium, allowing for greater data transmission rates and distances than conventional copper wire cables. This does not integrate incompatibility with standard cable ends to enhance speed.
A: A breakout cable is used in this case to make reference to an active optical cable assembly that breaks out a high-speed signal into several lower-speed signals. This is useful for networks like 40G QSFP to 10G SCP, which improve the deployment and configuration of networks.
A: Now that data rates are increasing and the demand for data centers is also on the rise, AOC cables have become fundamental because they are able to support the needed bandwidth as well as transmission distances. They have made a standard place in modern data centers because they can transmit at the required data rates over extended distances.
