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Difference between AOC & DAC cables Jul 09, 2018

DAC and AOC cables are widely applied in storage area network, data center, and high-performance computing connectivity, etc. Sometimes customers will make some mistakes between DAC & AOC cables, and feel confused about how to choose the cables for network construction.

DAC cable can be classified into direct attach copper cable and active optical cable . If a DAC contains the signal conditioning circuitry, it is an “Active DAC”. If not, it is a “Passive DAC”. For a Passive DAC to work, the host networking equipment must support the signal processing functions. Direct attach copper cables can either be passive or active, while AOC cables are always active. 

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DAC ( Direct Attached Cable) can be produced as passive and active, that is Passive Copper Cable and Active Copper Cable.

The passive DAC has no active components, it provides a direct electrical connection between corresponding cable ends. So it has minimal power consumption of <0.15w, but the linking distance is limited to 5m. While active copper cable (ACCs) contains electrical components in the connectors that can boost signal levels, allowing reaching greater distances (5m or more) via copper media and ensure better transmission quality. This makes active copper cables slightly more expensive and consumes more power than direct attach passive copper cables.

 

The AOC cable is always active. It has two types of connectors combined with fixed optical fibers with a similar function as optical transceivers. AOC cable is an alternative to optical transceivers, which eliminates the separable interface between transceiver module and optical cable.

Both DAC and AOC have their particular benefits and drawbacks. 

 

  • Advantages of Direct Attach Copper Cable

Cost saving -- Supporting such multiple protocols from Gigabit to 100G Ethernet, from up to 8G FC and InfiniBand, Direct Attach Cables (DAC) are a cost effective solution compared to optical transceivers. 

Interchangeability -- With the development of copper cable technology, DAC cable is interchangeable and hot swappable with optical modules.

Enough Data rate for various applications -- Today’s DAC can support higher data rates than old copper interfaces—from 4Gbps to 100Gbps per channel.

 

  • Disadvantages of DAC cables

The direct attach copper cable is heavy and bulky, making it difficult to be managed. Moreover, due to the nature of electrical signals, direct attach copper cable is vulnerable to the effects of electromagnetic interference (EMI), such as undesirable responses, degradation, or complete system failure.

 

  • Advantages of AOC cable

Lightweight -- Due to its material, AOC cable weighs lighter than DAC cable.

Longer distance -- Active Optical Cables’s length is up to 300 meters on OM3 MMF

EMI immunity -- Since the optical fiber uses light signals, AOC is immune to electromagnetic interference. 

Greater bandwidth -- Needing no equipment upgrades, AOC cable has a throughput of up to 40 Gbps with QSFP+.

 

  • Disadvantages of AOC

Compared with direct attach copper cable, the disadvantage of AOC cable is that it may be a little expensive for customers.