40GBASE QSFP+ AOC and 40GBASE-SR4 QSFP+ Transceiver, Which Is Your Choice?
Home Data Center 40GBASE QSFP+ AOC and 40GBASE-SR4 QSFP+ Transceiver, Which Is Your Choice?

40GBASE QSFP+ AOC and 40GBASE-SR4 QSFP+ Transceiver, Which Is Your Choice?

Posted on by FS.COM

Fiber optic transceiver as an integral part of overall system design, has been greatly improved in the past decades driven by the increasing needs for speed and performance. 40GBASE-SR4 QSFP+ transceiver which has small size and can support conversion between optical signals and electrical signals of high data rate, is now a commonly applied interconnection solution in data center for short distance. Meanwhile, an alternative for network interconnection is also catching our attention. This rising star is known as AOC (active optical cable), which is kind of DAC (direct attach cable) and can also support interconnection in data center.

A 40G AOC usually contains a length of fiber optic cable connected with QSFP+ connectors on both ends. 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. Compared with copper DAC, the interconnection relay on 40GBASE QSFP+ to QSFP+ AOC has more advantages in transmission distance, bend radius, cable size, cable weight and cable management. Compared with 40GBASE-SR4 QSFP+ transceiver, 40G AOC removed the need for fiber optic connectors and have a similar performance as the former, which seems to be a much more faster and easier methods for 40G interconnection. However, everything has its pros and cons. 40G QSFP+ AOC and 40G QSFP+ SR4 transceiver, which should be your choice? The following is offering the answer.


To figure out which one is more suitable for your applications, the comparison between the two components should be conducted from the following aspects: transmission distance, reliability, installation and maintenance, monitoring, and cost.

Transmission Distance

Optical signals are weaken as the transmission distance increases. Thus, to ensure the transmission quality, the transmission distance should be the first aspects to determine which one is better for your applications. Generally, 40G QSFP+ SR4 can support longer transmission distance than that of 40G QSFP+ AOC. For 40G transmission, if the distance is less than 100 meters, 40G QSFP+ AOC and 40G SR4 QSFP+ transceiver could have nearly the same performances. However, when the transmission distance is longer than 100 meters, the performance of 40G AOC will be limited. In this case, 40GBASE-SR4 QSFP+ will have a better performance. However, Fiberstore can provide 40G AOC supporting 40G transmission distance up to 300 meters.


Cables and connectors in data center inevitably need to be plugged out from devices like switches or servers for regular use and maintenance. With the actions of repeating plugging, the reliability and stability of a component became extremely important. The connectors of 40G AOC is factory pre-terminated, while QSFP+ SR4 transceivers is 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. In addition, there will be no insertion loss and return loss of 40G AOC, which can ensure its reliability furthermore. It has been proved that AOC has better reliability than that of transceivers.

Installation and Maintenance

Both 40G AOC and 40G QSFP+ SR4 transceiver are highly integrated components that provide increased port density and high data rate connection with great convenience during installation and maintenance. However, 40GBASE QSFP+ AOC is superior in this aspect. This is mainly because, it is factory pre-terminated. Just plug the connectors on the devices, the AOC can start working. It eliminates the process of linking two modules, which must be done for interconnection using 40G QSFP+ SR4 transceivers. Moreover, if there is a fault, you can just replace the AOC. However, the tests for the MPO connectors and cables are needed if 40G QSFP+ SR4 transceivers are used. Thus, AOC is easier and faster in installation and maintenance.

40GBASE-SR4 QSFP+ transceiver

Digital Diagnostic Monitoring

Digital diagnostic monitoring, shorts for DDM, is a function that most modern transceivers have. With this function the working performance of optics can be visually tested and controlled. No doubt that 40G QSFP+ SR4 has DDM function. The coupler state and sensitivity of this 40G transceiver can be adjusted to the best with the help of DDM. Currently, 40G AOC provided by the market doesn’t have such a strong function.

HP Compatible 40GBASE-SR4 QSFP+ Transceiver under testing


Choosing a solution for 40G interconnection, the cost must be considered from two main aspects. One is the material cost, the other is the maintenance cost. Currently the market price of 40G QSFP+ AOC is generally lower than 40G QSFP+ SR4 transceiver. To accomplish the connection, additional cost for patch cables should be considered for interconnection using 40G QSFP+ SR4 transceivers. For maintenance, as above mentioned, AOC is faster and easier which do not require much skills and saves labor. If the cost is limited, then AOC could be your choice.


After the comparison, it is clear that 40GBASE QSFP+ AOC is more reliable and stable than 40GBASE SR4 QSFP+ transceiver and costs less for 40G interconnection. However, it cannot perform as much good as 40GBASE-SR4 QSFP+ when the transmission distance is longer than 100 meters. And the function of DDM can help this  40G transceiver find its best working state, which is cannot be achieved by AOC. With these instructions, can you figure out which is the one you need? For better selecting, Fiberstore provides 40GBASE QSFP+ AOC and 40GBASE-SR4 QSFP+ transceiver in various specification for your reference. These modules and AOC can be trusted totally, cause they will be all tested before go to the market. Kindly contact sales@fs.com or visit FS.COM for more details.

Copyright © 2002-2018. All Rights Reserved.