Direct attach cable (DAC) and active optical cable (AOC) is crucial high-speed interconnect cabling solutions in data centers and high-performance computing applications. DAC and AOC cables are plug-and-play, allowing the users to optimize the existing network without new optical fiber cabling.

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Direct attach cable (DAC) and active optical cable (AOC) is crucial high-speed interconnect cabling
solutions in data centers and high-performance computing applications. DAC and AOC cables are
plug-and-play, allowing the users to optimize the existing network without new optical fiber cabling. This
article will discuss the differences between DAC and AOC cables.
DAC Cable VS. AOC Cable
DAC cable consists of a Twinax copper cable terminated with
SFP+/SFP28/QSFP+/QSFP56/QSFP28 connectors on both ends, which can provide an electrical
connection directly to active equipment. DAC cable can be passive or active. Passive and active
DAC cables can transmit electrical signals directly over copper cables. The passive DAC cable can
deliver without signal conditioning, while the active DAC cable has electric components inside the
transceivers to boost signals. AOC cable consists of a multi-mode fiber optic cable terminated

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with SFP connectors on both ends, which requires external power to complete the conversion of
electric and optical signals, from electric signals to optical ones, and then convert to electric
signals finally.
DAC and AOC cables differ from each other in the following aspects :
1. Power Consumption
Usually, the power consumption of an AOC cable is higher than a DAC cable, which is 1-2w. While
the power consumption of active DAC cables is less than 1w, and the passive DAC cables cost
nearly no power consumption at the value of lower than 0.15w due to the thermal design of DAC
cables. As a result, the operating expenses on power consumption will be decreased when
adopting the DAC options.
2. Transmission Distance
AOC cable can transmit over longer distances up to 100 m, while DAC cable link length limit is 10
m (passive DAC: 7 m; active DAC: 10 m). To sum up, DAC cable is suitable for short-range
transmissions, while AOC cable is used for long-range transmissions.
Note: the max. distance of a signal that can be transmitted via a DAC cable changes depending on

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the data rate. The link length will decrease as the data rate grows, for example, 100G DAC cables
can only transmit up to 5 meters.
3. Cost
In general, copper cables are much cheaper than fiber cables. When implemented in the
high-density data center, the sum of money will be saved for large quantities of DAC cable
compared to AOC cable.
4. Electromagnetic Interference Immunity
AOC cable is immune to electromagnetic interference, while DAC cable is vulnerable to the effect
of electromagnetic interference, such as unwanted responses, degradation, or complete system
failure.
5. Application
DAC cable is used to connect switches/servers to switches within racks and adjacent racks. In
other words, DAC cable is used as an alternative for ToR (top of rack) interconnections between
the ToR switch and server or the stacking of switches.

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AOC Cable is used to connect ToR switches to EoR (end-of-row) aggregation switches, and to
connect the ToR switch with MoR (middle-of-row) storage subsystems at reaches greater than
DAC cable limits of 3-7 meters.
Conclusion
DAC and AOC cables are simple, cost-effective cabling solutions that are designed for the same
ports as SFP+ or QSFP transceivers. DAC cable use copper-based cabling while AOC cable use
fiber-based cabling. DAC cable provides lower power consumption and is cheaper than AOC cable.
However, AOC cable provides long transmission distances than DAC cable. Sun Telecom
specializes in providing one-stop total fiber optic solutions for all fiber optic application industries
worldwide. Contact us if any needs.