Introduction to 100G QSFP28 DAC Cable

From providing flawless, high-flow media to real-time connectivity with customers around the world, today’s data centers require ultra-high speed. In order to provide a low-cost solution for data centers to connect switches, Ethernet switch vendors need to maximize the density of optical transceiver ports on their devices. This allows them to provide the maximum number of channels and the lowest cost per bit of traffic. The lowest cost of connecting 100G traffic is to use the 100G QSFP28 DAC Cable.

What is QSFP28 DAC?

QSFP28 DAC stands for 100G QSFP28 direct attach copper cable. 100G QSFP28 DAC is also called 100G QSFP DAC or 100G QSFP+ Copper Cable.
It is compliant with 100G Ethernet (100GBASE-CR4) specifications. So sometimes it is called 100GBASE-CR4 QSFP Cable. It contains four high-speed copper pairs, each operating at data rates of up to 25GbE. So the QSFP28 DAC cable assembly is suitable for power-efficient connectivity for short distance interconnects, such as data center, networking, and high-performance computing application.

What Is 100GBASE-CR4 ?

100GBASE-CR4 is one of the 100G Ethernet interface types. It is a standard of 100GBASE-R encoding and Clause 91 RS‑FEC over four lanes of shielded twin-axial copper cabling. It is defined as 4 x 25 Gb/s over copper cable per IEEE P802.3bj. 100GBASE-CR4 is different from 100BASE-KR4 that achieve 4 x 25 GB/s over the backplane. 100G QSFP28 DAC is 100GABSE-CR4 Cable that supports a max length of 5 meters.

QSFP28 DAC Types

QSFP28 DAC cable is available in two main types, QSFP28 direct attach cable and QSFP28 breakout copper cable.

TypesLengthConnectorDatarate
QSFP28 direct attach cable1M~5MQSFP28100Gb/s
QSFP28 to 4 SFP28 breakout cable1M~5MQSFP28-SFP28100Gb/s for QSFP28, 25Gb/s for SFP28

Fig 1. 100G QSFP28 to SFP28 Breakout Cable & 100G QSFP28 DAC

What is the difference between QSFP28 DAC and 100G QSFP DAC?

In fact, they are the same. Sometimes QSFP28 DAC is also called 100G QSFP DAC or 100G QSFP+ DAC. The “QSFP” form factor was originally defined for <10G speeds. When it was adopted for 40G, the name became QSFP+ to denote the higher aggregate performance. The same “QSFP” form factor was later adopted for 100G but the electrical interface had to be upgraded to handle 25Gbps/lane. The electrical interface for 100G can handle up to 28Gbps, hence the engineering and industry name is QSFP28.

In Conclusion

100G QSFP28 DACs delivers aggregate data bandwidth up to 100 Gbps (4x 25 Gbps) with passive copper assemblies. They provide an ideal solution that allows 100G switches and routers to be used within the data center, with low power consumption and a maximum port count. As a pioneer in 100G QSFP DAC, OPTCORE manufactures a wide line of 100G copper cables with high quality and very competitive pricing. We are ready to be one of a reliable vendor for data center player.

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