Your Quick Guide to QSFP28 to SFP28 Interconnect Solution

With the development of the increasing amount of connected 100G QSFP28 devices in the data centers and the demand for high-speed data processing, data centers need to get a strong ability to have a more quickly and efficiently transmit rate. In recent years, 25G SFP28 and 100G QSFP28 technologies are gaining more and more attention, by virtue of their ability to provide an efficient path to high-speed rates. So how to choose a suitable solution to connect 100GBASE Ethernet to 25GBASE Ethernet? This post will introduce four QSFP28 to SFP28 connection solutions.

What Is QSFP28 Transceiver Technology

The 100G QSFP28 form-factor first appeared in 2013. After several years of development, 100G QSFP28 optical modules have derived multiple categories, each with different optical module standards and suitable for different transmission applications. The QSFP28 form-factor provides four different signal channels, and the transmission rate is increased to 100 Gbps. The size of the QSFP28 optical module is smaller than the CFP, CFP2. If you want to deploy a high-density, high-speed network, QSFP28 optical module will be a good choice.

Four QSFP28 to SFP28 Interconnect Solution

QSFP28 to SFP28 Connection with MTP Breakout Cable

When directly connecting one 100G QSFP28 transceiver with four 25G SFP28 transceivers, an 8 fibers MTP to 4 x LC harness cable is able to do this job. This solution is suitable when the connected optics are arranged in short distances, like in the same rack/cabinet. MTP breakout cables provide the transition from multi-fiber cables to single fiber or duplex connectors. These cables are suitable for various applications with all network and equipment requirements, such as 100GB SFP modules. It provides a reliable, cost-effective, and efficient wiring system that can be used to migrate from traditional 25G to higher speed 100G Ethernet. For example, QSFPTEK's 4 LC Duplex MTP Breakout Cable can be used to connect four 25G QSFP28 and one 100G QSFP28.

Fig.1 - QSFP28 to SFP28 Connection with MTP Breakout Cable

QSFP28 to SFP28 Connection with 100G DAC Breakout Cables

100G QSFP28 DAC breakout cable, is widely used in equipment links within 5m of the rack. The 100G QSFP28 to 4x 25G SFP28 breakout direct attach copper cables’ one end is connected to a 100G port, and one end is connected to 4x 25G SFP28 ports it is an excellent solution to replace 100G optical modules for 100G Ethernet short-distance (1-5 meters) connections. If your 100GbE network is deployed in a 5m rack, the 100G QSFP28 to SFP28 DAC passive high-speed cable is very suitable for you. In terms of power consumption, DAC cables have lower power consumption than AOC cables. Since passive DAC cables do not require power, the power consumption is almost zero. Compared with 2W of Active Optical Cables, high-speed cables have certain advantages in terms of power consumption.

Fig.2 - QSFP28 to SFP28 Connection with DAC Breakout Cable

QSFP28 to SFP28 Connection with AOC Breakout Cables

100G QSFP28 Active Optical Cable includes 100G QSFP28 to 4x 25G SFP28 AOC, The 100G QSFP28 to 4x 25G SFP28 breakout Active Optical Cable’s one end is connected to a 100G port, and one end is connected to 4x 25G SFP28 ports, this cable length is 1-70M, QSFP28 to 4x 25G SFP28 AOC with OM3 cable maximum transmission distance is 70M; the maximum transmission distance with OM4 cable is 100M. It is mainly used in the interconnection of servers, storage devices, switches, and other equipment. By the way, the cost of using AOC will be higher than that of DAC. In addition to the price, AOC cable is also lighter and thinner than DAC cable and has a smaller minimum bend radius, which is conducive to the management of the cabling system.

 Fig.3 - QSFP28 to SFP28 Connection with AOC Breakout Cable

QSFP28-SFP28 Converter Module

QSFP28 Adapter (QSA) Module, offering 25 Gigabit Ethernet for 100G QSFP28-only platforms. It allows smooth and cost-effective migration to 100 Gigabit Ethernet by providing an option to use lower-speed SFP28 modules in empty QSFP28 ports or when the other end of the network is running at lower speeds. The QSA Module converts a QSFP28 port into an SFP28 port. With this adapter, customers can use any SFP28 module or cable to QSA Module to convert a QSFP28 port into an SFP28. With this adapter, customers can use any SFP28 module or cable to connect to a lower-speed port on the other end of the network. This adapter supports all SFP28 optics and cable reaches.

Conclusion

This post introduced four QSFP28 to SFP28 interconnect solutions. MTP breakout cable solution is used to directly connect one 100G QSFP28 transceiver with four 25G SFP28 transceivers, 100G QSFP28 to 4x25G SFP28 DAC breakout cable solution supports distance up to 5 meters within racks, and 100G QSFP28 to 4x25G SFP28 AOC breakout cable solution is used for 1 to 70 meters the distance between the switches to transmit 100G Ethernet data, the last 100G QSFP28 to SFP28 converter module is to use an adapter with SFP28 module or cable to connect to a lower-speed port on the other end of the network. The major differences between these four QSFP28 to SFP28 connection solution is shown in the below table:

When we choose a suitable Interconnect solution, we need to consider the cost, distance between the two ends of devices, device port density, and acceptable power consumption comprehensively. For example, if cost is your first consideration and the distance between the two ends of the device is within 5 meters, then 100G QSFP28 to 4x25G SFP28 DAC breakout cable solution may be your first choice. QSFPTEK provides a variety of 100G transceivers enabling cost-effective, high-density, and low-power 100G Ethernet connectivity solutions for data center, distribution layers, and service provider applications.