QSFP28 – A Better Way to 100G?

The fight over 100G component market has been upgraded with the emerging of 100G QSFP28. This is an optical transceiver which can support 100G with the transmission mode of 4*25G. Usually, the move before was considered to be 10G→40G→100G. However, the new roadmap of 100G with QSFP28 is 10G→25G→100G or 10G→25G→50G→100G. One has a lot of questions for 100G migration. Why does 100G QSFP28 appear? Can 100GQSFP28 change our data center? The below article has answers to all your questions regarding QSFP28.

 

What QSFP28 offers?

Cost and power are considered the most important factors in data centers. A look back to the evolution of 100G modules in the past years has shown that things keep changing, from CFP to CFP2 and CFP4. All these changes are closely related to factors like cost and power.

 

High Port Density: The first generation of 100G transceiver was CFP and the drawback was large size. Then CFP2 and CFP4 were the next generations of 100G modules with a decreased size (quarter width of CFP) as compared to former.  QSFP28 with the same footprint and faceplate density as QSFP+ is even smaller than CFP4. Up to 36 QSFP28 can be installed on 1RU switch on the front panel, higher port density being a big advantage.

 

Low Power Consumption: QSFP28 needs the lowest power consumption for transmission as compared with other 100G transceivers. It is less than 3.5 W whereas other transceivers consume around 6 W to 24 W.

 

Lower Cost: As seen above with higher port density and lower power consumption, the 100G QSFP28 be cost-efficient. Implemented with 4 lanes, this can increase the transmission capacity of every lane from 10G to 25G, which can effectively decrease the cost for each bit.

 

How could QSFP28 be a game changer for Data Center?

The 100G can be reached directly from 25G escaping 40G with QSFP28. We read how 100G uplink is converged by only four 25G links. In addition, the 25G network has the same cabling structure as a 10G network, but here capacity is much larger. The following table lists the related components and the suggested applications for QSFP28.

 

QSFP28 Series

 

Cabling

 

Applications

 

100G SR4 QSFP28

 

MMF,MTP/MPO

 

100G to 100G up to 100 m

 

 

 

100G LR4 QSFP28

 

SMF, LC Duplex

 

100G to 100G up to 10 km

 

100G QSFP28 to QSFP28 DAC

 

 

 

100G to 100G up to 5 m

 

100G QSFP28 to 4x25G SFP28 DAC

 

 

 

100G to 25G up to 5 m

 

100G QSFP28 AOC

 

 

 

100G to 100G up to 10 m

 

 

 

The challenge for long distance connectivity 

QSFP28 is the smallest 100G transceiver. It’s a fraction of the size of the CFP. It is best for short distances. However, for longer distances, there have been some recent breakthroughs in transceivers with DWDM capabilities. PAM4 being the most significant of all still requires amplification for every short distance. For distances over 5 to 6 km, needs dispersion compensation. With this, it can handle traffic up to 80 km.

 

While the need for connecting 100G traffic is growing, no single small transceiver can solve the problem of connecting switches between data centers and other longer distance sites. That’s why organizations consider full-blown, DWDM platforms to handle their 100G data center connectivity. Here the output of the QSFP28 transceiver is taken to run through a complex web of transponders, amplifiers, signal conditioning, multiplexers, and network management.

 

Conclusion

There are many ways to transmit to the 100G network. QSFP28 modules are the suggested methods till today but no one can tell what the future will like. Both IEEE and MSA have published standards for 100G QSFP28. Customers can select the range according to their applications. QSFP28 full family is now available at CBO.