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AOC vs DAC Cable: Which is Best for You

AOC Cable vs DAC Cable: Which is Best for You

Direct Attach Cables (DAC) and Active Optical Cables (AOC) are the up and coming contenders, growing in usage in the data center and enterprise networks. DACs and AOCs are plug and play, allowing existing cabling resources to turn up new connections without calling out specialized fiber optic or network engineering resources. DACs and AOCs are simply standard length cable assemblies with factory terminated transceivers on each end.

​DACs and AOCs come in a variety of configurations to meet network requirements. Each is available in 10G (SFP+), 25G (SFP28), 40G (QSFP+), and 100G (QSFP28) data rates with additional options for breakouts from 40G to 4x10G or 100G to 4x25G variants.

Transceivers with structured cabling are still commonly used, offering the most flexibility in deployment, however at dramatically higher costs. The ability to custom tailor a transceiver and structured cabling solution to the application is only limited by the budget and time to deploy.

Understanding the how DACs, AOCs or Structured Cabling address each of these needs will guide you towards the right cabling decision for your network.

Direct Attach Cables (DAC) and Active Optical Cables (AOC) are the two important cabling solutions in regards to interconnections in the data center and enterprise networks. Both AOCs and DACs are plug-and-play, allowing the users to optimize the existing network without a new optical fiber cabling. But the question is in what situation you should use DAC or AOC cable? What are the advantages and disadvantages of the two types of network cables? The following part of this article will make a brief explanation of these questions.



                                  ◮ DAC & AOC Cable Solution for IDC High-Speed Interconnect


1. What DO DAC and AOC Cables Have in Common?

Both DAC and AOC are common cabling solutions for data networking and are usually used for high-speed, high-reliability interconnection and transmission required by data centers, high-performance computers, and large-capacity storage devices. Both of their ends have cable assemblies with factory terminated transceivers, which are connected to fixed ports only. Besides, DAC and AOC cables can be manufactured in different lengths to support different transmission data rates, such as 10G SFP DAC/AOC cable, 25G AOC cable, 40G DAC cable, 100G AOC cable.

2.  Pros and Cons of DAC Cable 

Pros of Direct Attach Copper Cable

More Cost-effective— Generally speaking, the price of copper cables is much lower than that of optical fibers. The cost of passive copper cables is 2 to 5 times cheaper than fiber cables of the same length. Therefore, the use of high-speed cables will also reduce the cabling costs of the entire data center.

Lower Power Consumption— High-speed DAC (direct attach cable) consumes less power(the power consumption is almost zero) since passive cables do not require a power supply. The power consumption of active copper cables is generally around 440mW. If you use direct attach copper cables instead of AOC fiber cables, you can save hundreds of thousands of kilowatts of electrical power.

It is more durable–It is designed with a seamless connection form of optical module and optical cable, which reduces the cost and ensures that the optical port is not exposed to dust and other pollutants. Therefore, DAC is less susceptible to damage.

Cons of Direct Attach Copper Cable

One of the disadvantages of DAC cable is that it is heavier and bulkier than AOCs. In addition, it is more susceptible to the effect of electromagnetic interference and attenuation over longer distances due to the electrical signals transmitted between both ends.  

 

3. Pros and Cons of AOC Cable

Pros of AOC

Lighter weight-An active optical cable is composed of two optical transceivers and a fiber optic patch cable, whose weight is only a quarter of the direct attach copper cable, and the bulk is about half of the copper cable.

Longer distances-AOC fiber can provide a greater and longer transmission reach up to 100-300m due to its better heat dissipation in the computer room’s wiring system and smaller bending radius of optical cable.

More Reliable– Active optical cable is less vulnerable to electromagnetic interference since optical fiber is a kind of dielectric that can sustain a static electric field within it. The bit error rate of the product transmission performance is also better, and the BER can reach 10^-15.

 

Cons of AOC

The main defect of AOC active fiber cables is that it is a more expensive cabling assembly solution for high-density data center operators. Besides, AOCs are less durable if not managed properly since they are lighter and thinner AOCs are much lighter and thinner which makes them more susceptible to damage if not handled correctly. 



4. When do you Use DAC Cables?

According to the Frabic architecture announced by Facebook, a server and Top-of-Rack switches(ToR) constitute the basic unit of the data center. Generally speaking, the distance between a ToR and a server NIC(Network Interface Card) is less than 5 meters. In this situation, DAC cable is more advantageous than AOC cables in the respects of cost, power consumption, and heat dispersion. Thus, DAC is a preferred option to IDC interconnect systems. Besides, on some special occasions, 100G QSFP28 to 4*SFP28 DAC is an alternative direct connection according to the user’s specific demand for the data connection.

 5. When do you use AOC Cables?

Nevertheless, the transmission distance between ToRs and edge core switches is usually less than 100m, where Integrated circuits are deployed densely. Therefore, the active optical cable is a better cabling solution for data connection due to its merits of lightweight, small wire diameter, and manageable cabling maintenance. Since the data center has strict specifications on signal transmission, active optical cable is better than twin-ax DAC cable in signal integrity and optical coupling design, greatly reducing the errors in signal processing. Furthermore, the high-frequency EMI signal is processed within pluggable optical modules, AOC fiber cable has a better EMI performance than the DAC cable. Undoubtedly, AOC cable is your first option in the interconnection between switches and switches within short or intermediate reach.

Conclusion

It can be concluded that either active optical cables(AOC) or direct attach copper cables(DAC) are the better cabling solution for IDC networking according to different application demands. When there are few transmission requirements for the data center, the DAC cable solution is suggested as a better internet cable solution for the interconnection between the server and the switch within 5m/10m, while the AOC fiber solution is perfect for the interconnection between switches and the switches. By all means, it is unnecessary to analyze which is the better solution, that is AOC cable is always your first for performance is way much more important than cost if budget is never your concern.

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