Do You Know These Essential Information About QSFP28?

It’s known that 100G Ethernet will be widely used in the communications in 2017. So naturally, products about it are paid more attention, such as QSFP28 series. QSFP28 series is a relatively popular one, designed for 100G data rate and including QSFP28 optical transceivers, QSFP28 AOC&DAC. However, except that, do you know these essential information about it? Maybe you will ask what I mean for these essential information. Well, you will get it after reading this article.

For QSFP28 optical module, except that it’s a hot-pluggable optical module designed for 100G data rate, it integrates 4 transmitting and 4 receiving channels. And “28” means each lane carries up to 28G data rate. Meanwhile it can do 4x25G/2x50G/1x100G connection.

Of course, these information is just some basic information about it. The below is what we really should focus on.

For one thing, for most switches, QSFP+ can work on the QSFP28 ports. As we all know that QSFP28 optic fiber transceiver has the same form factor as the QSFP optical transceiver. The former has just 4 electrical lanes used as a 4x10GbE and 4x25GbE, while the latter supports 40G ( 4x10G). This is the same case as that the SFP28 optical transceiver can be connected with SFP+ optical transceiver and runs at the lower 10G speed.

In addition, the 100G QSFP28 port also can generally take either a QSFP+ or QSFP28 optic fibre module. And when using the QSFP transceivers on QSFP28 port, both single-mode and multimode (SR/LR) optical transceivers and twinax/AOC options are available.

For another thing, in all cases, QSFP28 optical transceiver cannot be used on QSFP+ port. To some degree, SFP+ can’t auto-negotiate to support SFP module. Similarly, QSFP28 optical modules can not be used on the QSFP port, either. Besides, there is the rule about mixing optical transceivers with different speed: both ends of the two optical modules and form factor have to be connected.

Finally, in the aspect of  its applications, we have to realize the fact ,currently, the QSFP28 optical transceiver in the market can only support up to 10 km (QSFP28 100GBASE-LR4) with WDM technology. While for applications beyond 10km, it cannot reach it. After all 100G technology and relevant optical module are still under development even if it’s widely used in the market.

In a word, although QSFP+ modules can be used on the QSFP28 ports, and it cannot transmit 100Gbps on the QSFP+ port and still have some limitation in transmission distance. If you want to know more about it, welcome to contact us at any time.