40G QSFP+ AOC vs. 40G QSFP+ SR4 Transceiver

With an increasing demand for higher performance and flexibility, fiber optic transceiver has been greatly improved in the past decades driven by the increasing needs for speed and performance. 40G QSFP+ SR4 transceiver that can support conversion between optical signals and electrical signals of high data rate, has become a widely used interconnection solution for short-reach applications in data center. At the same time, active optical cable (AOC), a rising star used for short-range multi-lane data communication and interconnect applications is also drawing our attention.

40G AOC, is a type of active optical cable for 40GbE applications that is terminated with 40GBASE-QSFP+ on one end, while on the other end, in addition to QSFP+ connector, it can be terminated with SFP+ connector, LC, SC, FC, and ST connector etc. 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 do you prefer? This article will compare them from the following aspects.

Transmission Distance

Optical signals become weaker as the transmission distance increases. In general, 40G QSFP+ SR4 can support longer distance than 40G QSFP+ AOC. In 40G transmission, for distances less than 100 meters, 40G QSFP+ AOC and 40G SR4 QSFP+ transceiver nearly have the same performances. However, when the transmission distance is longer than 100 meters, the performance of 40G AOC will be limited.


With the actions of repeating plugging, the reliability and stability of a component is extremely important. The connector of 40G AOC is factory pre-terminated, while QSFP+ SR4 transceiver is connected by additional MPO connectors and fiber optic cable. Thus, compared with QSFP+ SR4 transceiver, AOC is less affected by the repeating plug in daily use. Besides, 40G AOC causes no insertion loss and return loss, which is an outstanding advantage. Thus, the reliability of 40G AOC is better than QSFP+ SR4 transceiver.

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. AOC can work only by plugging the connectors on the devices. 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 to install and maintain.

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.


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 that of 40G QSFP+ SR4 transceiver. To accomplish the connection, additional cost for patch cables should be considered for interconnection using 40G QSFP+ SR4 transceivers.


From the above analysis, we can see that 40GBASE QSFP+ AOC is more reliable and stable than  40G QSFP+ SR4 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, FS.COM provides 40GBASE QSFP+ AOC and 40G QSFP+ transceivers. Beside, MPO cable and MTP cable for 40G Ethernet are also available for your choice.

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