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01 Aug 2016

Direct attach cable, short for DAC, is a form of high speed cable with “transceivers” on either end. They can be used to connect switches to routers or servers. They are becoming increasingly popular in the network industry and widely applied in storage area network, data center, and high-performance computing connectivity etc. The DAC has the advantage of cost-effectiveness compared with the regular optics. Another reason for its increased popularity is that RJ-45 10G is not widely adopted, and most high density 10G switches are delivered with 48x SFP+ ports in 1 Rack Unit. Here are some basic knowledge you may not know but should know about the DACs.

Cisco SFP-H10GB-CU5M

1. No matter in the related article or in product description of some DACs vendors, there is always a point saying that the active DACs are lighter and thinner than passive DACs. Actually, it is a wrong view of point. If you have an using experience of both active and passive DACs, you may find that there is no difference between them in the weight and appearance.

2. As the first point mentioned, the thickness and weight do not depend on the active or passive function. In fact, they are divided according to their characteristic of AWG (American Wire Gauge). For instance, AWG24 DAC is thicker and heavier than the AWG30. Because of the difference of wire diameter, the longer the cable, the more inconvenience AWG24 DAC is, compared with the AWG30. Moreover, there is also limited bend radius. Thus, the longer the distance, the higher the AWG rating should be.

3. When the transmission distance is over 5 metres, active DAC is more suitable than passive DAC. Because it will cause the signal issue when using passive DAC for long-haul transmission.

4. DACs are more cheaper than the regular optics. Because the “transceivers” on both ends of DACs are not real optics. Compared with the regular optics, they are without the real components and just used to transmit the optical signals. And of course, without those expensive optics components, the cost of DACs is much lower. Thus, though using the same port as an optical transceiver, DACs are with significant cost savings and power savings in short reach applications.

5. The main difference between active DAC and passive DAC is that there is a driving chip in the design of active DAC.

6. AOC (Active Optical Cable) is one of the form of DAC which integrates multimode optical fiber, fiber optic transceivers, control chip and modules. With the benefits of AOCs, such as lighter weight, high performance, low power consumption, low interconnection loss, EMI immunity and flexibility etc. AOCs are now considered as the rising star of telecommunications and datacom transceiver markets.

Direct attach cable assemblies, including copper (DAC, direct attach copper cable) and fiber (AOC, active optical cable) types, are mainly used as media to support high transfer rates between servers, switches and storage devices intra rack or inter rack in a data center. FS.COM offers a variety of high speed interconnect DAC assemblies including 10G SFP+ cable, 40G QSFP+ cable, and 120G CXP cable to satisfy the demands from 10G to 100G interconnection. All these direct attach cables can meet the ever growing need to cost-effectively deliver more bandwidth, and can be customized to meet different requirements.


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