Tag Archives: AOC


40GBASE-SR4 QSFP+ transceivers is now being widely used for 40G network interconnection in short distance. This is a highly integrated component which has small size and uses four channels to support conversions between optical signals and electrical signals over a high data rate up to 40G. However, another component which can replace this transceiver in network interconnection becomes popular in data center application. It is 40GBASE QSFP+ AOC (active optical cable).

AOC is a kind of direct attached cable (DAC), which is available in 10G, 40G and even 120G. 40GBASE QSFP+ AOC contains a QSFP+ connector on one end and one QSFP+ connector on the other end which are linked by a length of fiber optic cable. There are also fanout versions of 40GBASE QSFP+ AOC with one end connected with a QSFP+ connector and the other end with several SFP+/XFP connectors. It looks like a fiber optic patch cable, but, it has a similar function of optical transceiver, and also can transmission signals with its fiber optic cable. 40G AOC removes the process of two modules, which must be done in a 40G interconnection using 40G SR4 QSFP+ transceiver. It seems that both 40G AOC and 40G transceiver are good solutions for interconnection. However, everything has it’s Pros and Cons. Figure out the one that fits your application is the most reasonable way. The following is to offer comparison between these two components for your references.


Transmission Distance: The first aspect to be considered is the transmission distance of these two components. Currently the 40G transmission is usually used in backbone network. Thus, to assure the transmission quality, distance should be ensured. Both 40GBASE-SR4 QSFP+ and 40GBASE QSFP+ AOC are designed for 40G transmission in short distance. Generally, when the distance is shorter than 100 meters, the two have similar performance. However, when it’s longer than 100 meters, AOC cannot perform as good as transceiver. Currently most 40G AOC provided by the manufacturers are less than 100 meters. However, Fiberstore can provide 40G AOC up to 300 meters.

Reliability: In work state, both of the components should be inserted into a switch or server. And the repeating plug of them are necessary for daily use and maintenance. It is known to us that, these actions might affect the performances of the component. Thus reliability of these components should be considered. The connectors of 40G AOC are factory pre-terminated, while QSFP+ SR4 transceivers are connected by additional MPO connectors and fiber optic cable. Thus, compared with QSFP+ SR4 transceiver, AOC is less affected by the repeating plug during daily use. It has been proved that AOC has better reliability than that of transceivers.

Installation and Maintenance: it has been clear that 40G AOC is much easier during installation, as the connectors have already terminated in factory. Customers just need to plug the two connectors in the switches, then can start working. While, for 40G SR4 QSFP+, additional patch cords with MPO connectors are used to finish the link. If there is a fault in the interconnection, for AOC, you can just replace it with another AOC. However, for interconnection using 40G QSFP+ SR4 transceivers, you have to locate the fault firstly by testing the patch cords and optics.

40GBASE-SR4 QSFP+ transceiver under test

Digital Diagnostic Monitoring (DDM): to achieve the best working state, most modern transceivers are armed with DDM function. With it, the working states and performance of the optics can be visually controlled. No wonder that 40GBASE-SR4 QSFP+ has such function. However, 40G AOCs that are provided by the market now do not have it.

Cost: two main aspects should be considered in selection a product in data center. One is the material cost. The other is the maintenance cost in the daily use. AOC has advantages over transceivers on both aspects. The price for 40G AOC is generally cheaper than 40G QSFP+ SR4. In addition, the interconnections reply on 40G transceivers also need additional fiber optic cables. The latter aspect has been clearly illustrated in the above. AOC can save more in general.

In conclusion, 40GBASE-SR4 QSFP+ can achieve best working status by using DDM and it has better performance when the transmission distance is longer than 100 meters. While 40GBASE QSFP+ AOC is cheaper, easy to manage and test, and it has similar performance as the former does over transmission distance less than 100 meters. For your reference, Fiberstore offer a wide range of both 40GBASE-SR4 QSFP+ and 40GBASE QSFP+ AOC. You can trust all of them cause they are all be tested before they go to the marker. Kindly contact sale@fs.com or visit FS.COM for more detail, if you are interested.

Active Copper Cable—Economical Interconnection Solution

In today’s data center, direct attached cable (DAC) is widely used for interconnection. With 40G migration, DAC becomes more popular, because they can support the high data rate and complete the interconnection in short time effectively. Currently, there are three types of DACs: passive copper cable, active copper cable and active optical cable (AOC). However, different DAC have different performances and prices. Passive or active? Copper or optical? Which DAC is the one you need?

In data center, the battle between performance, transmission distance and cost has never ended. This is also true to the selection of DAC for 40G data center interconnection. To find a cost-effective 40G DAC solution for data center interconnection with reliability and stability, this article will provide you the solution by several rounds of battle between the three types of DAC.

active copper cable connection

Battle Over Transmission Distance

The first round of battle is transmission distance which is always the first factors to be considered during the selection of DAC. This is because it is closely related to the transmission distance. There is no wonder that optical cable can transmit signals over longer distance than that of the copper cable. When the data rate required for interconnection is less than 5 Gbps, the passive copper cable is usually used for interconnection in data center. However, they can only support 40G transmission over really short distance. Optical cable is used to overcome the challenge of the distance. Supported with connectors that are embedded with electronics/optics, 40G active optical cable can support 40G transmission up to 100 meters. Active copper cable can support 40G transmission over copper cable up to 15 meters with QSFP+ connector embedded with electronics. In the battle over transmission distance, optical active cable wins without doubt.

Battle Over Power Consumption

The connectors attached with AOC and active copper cable are the main reason why the two cables can support 40G transmission over longer distance than that of passive copper cable. AOC which can support the longest 40G transmission distance is with the highest power consumption—more than 2W. The power consumption for active copper cable is only 440mW. However, passive copper cable requires no power during the transmission. In this battle, passive copper cable wins and AOC lost its advantages and is in the third place.

Battle Over Cooling

Cooling is closely related to data center reliability and life of use. The DAC in the data center can also affect the cooling of data center. The cable size and power consumption will directly influence the cooling efficiency of the data center. The thinner the cable is, the better dispersion devices in data center would have. Among the three types of DACs, optical cable is the thinnest among the three types of DAC. Active copper cable is also thinner than passive cooper cable. Active copper is also thinner than passive cooper cable. As mentioned, AOC has the highest power consumption and active copper cable has a lower power consumption, while passive copper cable requires no power. In this round of battle, it’s hard to tell which one wins. It depends on the practical and specific situations in the data center.

Battle Over Cost

It is clear that copper is much cheaper than optical cable. AOC, with connectors embedded with electronics and/or optics is the most expensive one. AOC is strongly recommended if cost is not a problem. It has the best transmission performance. However, for many data centers, it’s hard to have an ideal situation like this. Cost sometime can determine the final decision of the choice in data center cabling. Most of the components in data center are expensive and require careful maintenance. Passive copper cable is much cheaper than AOC. However, it cannot support 40G transmission in most cases in data center. Active copper cable is less expensive than AOC and can support longer transmission than passive copper cable seems to be a good choice.

Active Copper Cable—Economical Interconnection Solution


After several rounds of battle, the price and performances of the three DACs are clear. What to be considered next is the practical application. After several rounds of battle, the price and performances of the three DACs are clear. What to be considered next is the practical application. In most data center, most server to server connections require 2-5 meters, while rack to rack connections are required to be connected by 8-12 meters cables. For 40G transmission, the application of passive copper cable is limited because it only supports really short transmission distance. AOC has the best transmission performance. However, it costs most in both material and daily use. It’s expensive and needs more power. And in daily maintenance, they need careful management, because the optical cables are fragile. If cost is not a problem, then AOC is suggested for 40G transmission.

What to be considered next is the practical application. In most data center, most server to server connections require 2-5 meters, while rack to rack connections are required to be connected by 8-12 meters cables. Due to the Active copper cable, which is less expensive and can support 40G transmission up to 15 meters with low power consumption, can satisfy the regular interconnection requirement for distance and cooling in most data center. For the cost, you also don’t need to worry about, as it is much cheaper than AOC and it is stronger than AOC during cabling and daily maintenance. If you are looking for an economical solution to upgrade your data center to 40G, then active copper cable won’t let you down. The following chart can illustrate the advantages of active copper cable clearly.

DAC Type 40G Transmission Distance Power Consumption Price
Passive Copper Cable 5m Reach 0W Inexpensive
Active Copper Cable 15m Reach 440mW Moderately Priced
Active Optical Cable 100M+ Reach 2W+ Expensive

FS.COM provides a full range of 40G active copper cables of high quality. All the connectors and cable lengths can be customized according to your applications. You contact sales@fs.com for more details.