Posted byVijay Gupta14/05/20200 Comment(s)

A direct attach cable (DAC) is used to connect one mobility access switch with another when forming a stack, which can be either passive or active. Since the passive DAC cable contains no active components, it provides a direct electrical connection between corresponding cable ends. This process can also be done by an active DAC cable that is considered active because there are optics and/or electronics embedded within the connectors. Active DAC vs. passive DAC: the active one helps to improve signal quality and provides a longer cable distance. The DAC cable is a fixed assembly that is purchased at a given length.

From the material of the cable, DAC cable can be classified into direct attach copper cable and active optical cable (AOC). Direct attach copper cables can either be passive or active, while AOC cables are always active, as two kinds of commonly used transceiver assemblies, both direct attach copper cable and AOC cable have their advantages and disadvantages.


Active Optical Cables

AOCs are lightweight in design and just like DACs, widely applied in storage area networks, data centres and high-performance computing connectivity’s. AOCs use light signals and are not able to conduct an electric current thus making them immune to electromagnetic interference.


Advantages of AOC:

Higher Bandwidth: Without any equipment upgrades, AOCs have a throughput of up to 40Gbps with QSFP+.

Cable Bend Radius: The cables of AOCs are thin and have a significant bend radius making AOCs the optimal solution if data centres don’t have enough space for cabling.

Air-flow and cooling: Due to the AOC cable being thin in design, the switches will have more room for air flow and easy for cooling system.


Direct Attach Cables

DACs contain a passive component and are used to connect one mobility access switch with another when forming a stack. DACs also provide a direct electrical connection between corresponding cable ends and have enough data rate for various applications and support higher data rates than a traditional copper interface, from 4Gbps to 10Gbps per channel. 


Advantages of DAC:

Cost Affordable: When implemented in a large data centre, DACs can significantly reduce costs over same length AOCs.

Lower power consumption: DACs cooling requirements are not strict due to their thermal design which lowers power consumption and decreases data centre operating expenses.

Reliability and faster transmission: The mean time between failures (MTBF) is about 500 million hours making them reliable with fast transmission. This MTBF makes DACs essential for data centres.

Flexible operating temperature: DACs don’t produce heat thus making it a more versatile product that can be used in wider temperature ranges.

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