Active And Passive DAC Twinax Cable Comparison

To accommodate the improvement of data transmission between the serves and switches, DAC cable has been developed. Direct Attach Cable (DAC) assembly is a high performance integrated duplex data link for two-directional communication over optical or copper cable for lengths up to 50 m. Twinax cable is a kind of cable which contains two semi-conductors. That is different from coaxial cable which has only one semi-conductor within it. Nowadays, twinax cables have been widely used in many short-range high-speed differential signaling applications.

There are two classifications of DAC cable—source and transmission speed. Copper twinax cable and Active Optical Cable (AOC) is two kinds of DAC cable. Within or without electrical components, active and passive copper cable are further divided. According to transmission speed, there are 10G, 25G, 40G and 100G DAC cables. So what are the main differences between active and passive DAC twinax cable? In the following text, we will provide a perfect answer to you.

The Main Differences

Most commonly, the differences between active and passive DAC twinax cable mainly lie in link length, inner components, and appearance.

• Link Length—A passive DAC twinax cable carries a Ethernet signal over short length (0.5 m-5 m). An active DAC twinax cable carries a Ethernet signal over long length (5 m-10 m). For example, The link length of Cisco SFP-H10GB-ACU3M is longer than Cisco SFP-H10GB-CU3M. Just shown as the below picture.
• Inner Components—The major difference between active and passive DAC twinax cable is whether they contain electrical components to boost signal strength or not. An active copper cable contains electrical components in the connectors that boost signal levels while a passive one has not.
• Outer appearance—The active and passive copper cable could not be distinguished from the outer appearance. They have the same connectors and cable jackets.

Link length and signal strength are two principal factors when people select an appropriate cable. But how to select an optimal one really depends on your real demand. If you are looking for a cable for short link length, passive DAC cables is highly recommended. When the transmission distance exceeds 5m, active DAC twinax cable is the perfect solution with steady signal strength.

How to choose more economically?

In addition to signal power and transmission distance, cost also plays a dominating part in guiding people how to select. Like we noted before, an active copper cable contains electrical components, which makes it more expensive than a passive one. A 1m 40G QSFP+ active copper cable is $110, while a 1m 40G QSFP+ passive copper cable is $46 on FS.COM. So the price is just within a slight difference. Which one is your cup of tea? Here, we provided a solution to ease your allodoxaphobia. An advanced QSFP+ 16-Port Switch (about $9450) with a 40G QSFP+ passive DAC twinax cable ($46 each) amounts to a basic QSFP+ 16-Port Switch (about $8426) with a 40G QSFP+ active DAC twinax cable ($110 each). The total cost is equal. In this way, you can select a suitable match.

Summary

According to this passage, we are cleared that the major differences between active and passive DAC twinax cable lie in link length, electrical components and cost. You can have you own choice based on you need.