Direct Attach Cable Buyer's Guide 2026: How to Choose DAC vs AOC for 10G–200G Data Centers | Hirundo

Data centers are being stretched to their limits. Hyperscale cloud platforms, AI training clusters, and enterprise networks all demand faster, denser, and more power-efficient interconnect solutions at every layer of the architecture. For links that run from 10G up to 200G and cover relatively short distances inside a facility, two cabling options dominate the conversation: Direct Attach Cables (DAC) and Active Optical Cables (AOC). Choosing between them — and choosing the right variant — has a direct impact on port density, thermal load, link reliability, and total cost of ownership.

This buyer's guide explains what DACs and AOCs are, how they differ, and how to select the right cable for 10G, 25G, 40G, 100G, and 200G data center interconnect. It also highlights how Hirundo's DAC/AOC portfolio supports data rates from 10G to 200G with low power consumption, a small footprint, and high reliability.

What Is a Direct Attach Cable (DAC)?

A Direct Attach Cable is a fixed, factory-terminated assembly that connects two network ports directly, without separate pluggable optical modules. Both ends carry a permanently attached transceiver-style connector — typically QSFP56, QSFP28, QSFP+, SFP28, or SFP+ — so the assembly plugs straight into the switch, server, storage, or router port. This "no separate module" design removes one layer of components, cutting both cost and insertion points.

Passive DAC

A passive DAC uses only copper twinax wire to carry the electrical signal and contains no active electronics. That makes it the lowest-cost and lowest-latency option, with essentially no power draw. Because electrical signals degrade quickly over copper, passive DACs are normally limited to short runs — commonly 1 to 5 meters — which makes them ideal for connecting servers to top-of-rack switches within the same rack or row.

Active DAC

An active DAC adds a small signal-conditioning chip inside the connector housing. This equalizes and re-drives the electrical signal, extending reach to roughly 10 meters while keeping cost and power far below an optical solution. Active DACs are a sensible middle ground when a passive cable is just slightly too short for the run.

What Is an Active Optical Cable (AOC)?

An Active Optical Cable replaces the copper conductor with optical fiber and uses electrical-to-optical conversion at each end. Because light travels with far lower loss than electrical signals, AOCs support much longer distances — up to 100 meters and beyond — while remaining immune to electromagnetic interference (EMI) and crosstalk. They are also significantly lighter and thinner than copper assemblies, which simplifies cable management and improves airflow in dense racks. At the highest rates, such as 200G QSFP56, AOC designs use four-level PAM4 modulation per lane to pack more bits into the same bandwidth.

DAC vs. AOC: Key Differences at a Glance

The table below summarizes how passive DAC, active DAC, and AOC compare across the criteria that matter most to network planners.

How to Choose the Right Cable

Use the following six criteria to narrow down the correct assembly for each link in your network.

1. Data Rate

Match the cable to the port speed. Hirundo's DAC/AOC series covers the whole 10G to 200G range, including 10G SFP+ to SFP+, 25G SFP28 to SFP28, 40G QSFP+ to QSFP+, 100G QSFP28 to QSFP28, and 200G QSFP56 to QSFP56. Breakout options such as QSFP28 to 4×SFP28 and QSFP+ to 4×SFP+ let a single high-speed port feed four lower-speed servers.

2. Reach and Distance

Count the actual meters between endpoints, then add a service loop. If the run stays inside a single row, a passive DAC is usually the most economical choice. If it crosses rows or exceeds roughly 10 meters, an AOC becomes the practical solution.

3. Connector and Cable Type

Confirm the port form factor on both ends. Available types include QSFP56 to QSFP56, QSFP28 to QSFP28, QSFP28 to 4×SFP28, QSFP+ to QSFP+, QSFP+ to 4×SFP+, SFP28 to SFP28, and SFP+ to SFP+. Standard lengths run from 1M, 3M, 5M, and 15M up to 30M and 100M, with custom lengths available.

4. Copper Gauge for DAC

For copper assemblies, the American Wire Gauge (AWG) affects flexibility and signal integrity. Thicker 24AWG cable carries signals farther but is stiffer, while 26AWG, 28AWG, and 30AWG options are thinner and easier to route in high-density racks.

5. Fiber Type for AOC

For multimode AOC, choose OM2, OM3, OM4, or OM5 fiber based on the required reach and speed. Newer grades such as OM4 and OM5 offer greater bandwidth for higher data rates over longer distances. Wavelength options include 850nm, 1310nm, 1550nm, 1270/1330nm, and CWDM, LWDM, MWDM, and DWDM channels.

6. Brand Compatibility

Because DAC and AOC assemblies are typically coded for a specific switch vendor, compatibility is essential. Hirundo products are offered for Generic, HUAWEI, H3C, CISCO, RUIJIE, ZTE, NOKIA, HP, MELLANOX, Arista, and DELL platforms, and special coding can be arranged on request. Assemblies are built around widely recognized form factors and are engineered to align with international standards such as IEEE 802.3, ITU-T, and IEC.

Hirundo's DAC and AOC Series: Built for 10G–200G Data Centers

Hirundo's AOC/DAC series covers the full 10G to 200G range. Low power consumption, a small size, and high reliability help increase data center capacity, improve port density, and reduce power consumption. These cables are mainly used for the internal interconnection of data centers — linking servers, switches, storage, and routers inside the facility.

For high-speed modules, Hirundo's AOC offerings include the 200G QSFP56 to QSFP56 AOC and the 10G SFP+ to SFP+ AOC, both designed for reliable, low-power operation in densely packed data center environments. Whether you are refreshing a 10G access layer or deploying a 200G spine, the same family approach keeps sparing, testing, and service consistent across the network.

Conclusion

There is no single "best" cable — only the best cable for a given link. Passive DAC wins on cost, latency, and simplicity for very short in-rack connections. Active DAC extends that copper approach a little further when signal condition is needed. AOC delivers the reach, EMI immunity, and light weight required for longer, denser, and higher-speed runs up to 200G. By matching data rate, distance, connector type, fiber grade, gauge, and vendor compatibility, network planners can build a cleaner, cooler, and more scalable cabling infrastructure — and Hirundo's DAC/AOC series is ready to support that build from 10G all the way to 200G.