From providing flawless, high-flow media to real-time connectivity with customers around the world, today's data centers require ultra-high-speed data transmission, promoting the development of the whole optical communication market. 100G QSFP28 cable is a necessity for data transmission. 

How many types of 100G QSFP28 cables are available on the market and what are they? Find answers in this article. 

100G QSFP28 Cables Basics

100G QSFP28 cable contains two forms: one is a form of high-speed cable with 100G QSFP28 connectors on either end, transmitting and receiving 100Gbps data over a thin twinax cable or a fiber optic cable, and the other is a form of breakout cable that can split one 100G signal into 4x 25G (100G QSFP28 to SFP28) or 2x 50G, enabling connectivity between network devices with different speed ports, while fully utilizing port bandwidth.

Data Rate
Connector Type
Cable Type
100G DAC (Direct Attach Cable)
QSFP28 to QSFP28
Passive Twinax Copper Cable
100G DAC Breakout Cable
QSFP28 to QSFP28 / QSFP28 to SFP28
Passive Twinax Copper Cable
100G AOC (Active Optical Cable)
QSFP28 to QSFP28
Optical CableOM3)
100G AOC Breakout Cables
QSFP28 to QSFP28 / QSFP28 to SFP28
Optical CableOM3)

1. Types of 100G QSFP28 Passive Direct Attach Cable DAC

Generally speaking, there are two kinds of 100G DAC cables: 

100G Active DAC and 100G Passive DAC. 

And 100G Passive DAC is generally divided into three types: 

  • 100G QSFP28 to 100G QSFP28 Passive Direct Attach Cable DAC
  • 100G QSFP28 to 4× 25G SFP28 Passive Direct Attach Cable DAC
  • 100G QSFP28 to 2x 50G QSFP28 Passive Direct Attach Cable DAC

 100G QSFP28 to 100G QSFP28 Passive Direct Attach DAC Cable

100G QSFP28 to 100G QSFP28 Passive DAC is a 4-channel parallel passive copper cable that combines four 28 Gbps SFP channels into one high-density cable. It offers 4 independent data transmitting channels and 4 data receiving channels via copper cable, providing a cost-effective way to establish a 100-Gigabit link between QSFP-100G ports of switches within racks and across adjacent racks, ideal for data centers, high-end servers and enterprise wiring closets. QSFP28 DAC is usually applied for Top of Rack (ToR) interconnections between 100G ToR switch and server or the stacking of 100GbE switches (as the figure below).

100G QSFP28 to QSFP28 DAC:

  • Suitable for stacking, cascading and direct connection between short-distance 100G devices, such as 100G switch, etc.
  • It can provide customers with 100g high bandwidth data interconnection capability and 4-way duplex channels. The working rate of each channel can support 25gb / s, and the convergence bandwidth is 100GB / s.
  • In accordance with sff-8436, it is applied to the connection between devices with qsfp28 port.

100G QSFP28 Passive Direct Attach DAC Cable

100G QSFP28 to 4*SFP28 Passive Direct Attach  DAC Cable is a breakout cable providing a hybrid transition from a 100G QSFP28 on one end to four individual SFP28 on the other end. It offers four parallel, bi-directional channels each operating at up to 25Gps. Featuring low crosstalk, small bend radius and low power consumption, the 100G to 25G breakout cable meets the ever-increasing demand for higher channel density with high-level signal integrity in high-performance computing, top-of-rack switching, and network storage deployments.

100G QSFP28 to 4*SFP28 DAC:

  • Applicable to interconnection between 100G and 25G equipment.
  • One end is 100G QSFP28 interface, the other end is four 25G SFP28 interfaces, which can provide customers with 100G high bandwidth data interconnection capability.
  • In accordance with SFF-8665/SFF-8679、IEEE 802.3bj and InfinibandEDR standard.
  • Provide a distance range of 1-5m, widely used in data center or Supercomputing Center system scenarios

                                        100G QSFP28 to 4× 25G SFP28 Passive Direct Attach DAC Cable

100G QSFP28 to 2x 50G 100G QSFP28 breakout Direct Attach  DAC Cable is a 4-channel parallel copper direct attach cable offering 4 independent data transmission channels and 4 data receiving channels via the cable. The aggregate data rate of 100Gbps over 5m transmission can be achieved with this product. Designed for use in cost-effective 100GbE to 2x 50GbE Ethernet connectivity solution to meet the growing needs for higher bandwidth in data centers, this 100G QSFP28 cable is suitable for the Infiniband EDR and 128G Fiber Channel.

In short-distance transmission, DAC high-speed cable has the advantages of low power consumption, low cost and convenient use. Choosing the right cable in different scenarios can achieve better results. It is widely used in the Internet data center. ETU-Link can provide 100g qsfp28 DAC high-speed cable with reliable quality and high cost performance, which can meet the growing cabling requirements of transmission rate, scalability and reliability.

2. Types of 100G AOC Active Optical Cable

AOC (Active Optical Cable) is a communication cable that needs to use external energy to convert electrical signals into optical signals or conversely in the communication process. There are commonly two types of 100G AOC: 100G QSFP28 to 100G QSFP28 AOC and 100G QSFP28 to 2x 50G 100G QSFP28 AOC.

Application of 100G QSFP28 AOC Active Optical Cable

100G QSFP28 to 100G QSFP28 AOC

100G QSFP28 to 100G QSFP28 AOC cable is composed of multi-mode optical fiber and parallel optical modules. The 100G QSFP28 transceivers at both ends provide photoelectric conversion and optical transmission functions to increase the transmission rate and distance of the optical cable without weakening the compatibility with the standard electrical interface. With no insertion loss and return loss, 100G AOC is mainly used for short-distance multi-channel data communication applications in several locations in the data center like ToR, EoR and MoR (as the figure below).

100G QSFP28 to 4x 25G SFP28 AOC Active Optical Cable

100G QSFP28 to 4x 25G SFP28 breakout AOC is a high data rate parallel AOC, to overcome the bandwidth limitation of traditional copper cable, terminated with a 100G QSFP28 module at one end and 4*SFP28 modules at the other. It provides a cost-effective solution for data center interconnecting using devices with 100G QSFP28 ports and 25g SFP28 ports, which is also ideal for High Performance Computing (HPC) and network storage deployments.

100G AOC Breakout Cables

 FAQs About 100G QSFP28 DAC Cable/AOC Cables

1. What is the difference between 100G DAC Cable and AOC cables?

A: 100G QSFP28 DAC (Direct Attach Cable) is composed of Twinax copper cables with connectors on both ends, while 100G QSFP28 AOC is MMF cable with SFP connectos on both ends. There are several differences between these two cables. In general, 100G QSFP28 DAC (Direct Attach Cable) consumes less power and is more cost-effective than 100G QSFP28 AOC. By contrast, 100G AOC supports higher performance in transmission distance and is also more suitable for data center deployment. 

2. Q: What is the structure of 100G QSFP28 AOC cables?

A: 100G QSFP28 AOC mainly consists of two optical modules and an optical cable jumper. The transceivers at both ends are composed of different lengths of OM3 or OM4 multimode fiber.

3. Q: Can 100G QSFP28 cables be used for 40G?

A: Yes, 100G QSFP28 cables can be used for 40G, but not vice versa. There is a rule about mixing optical transceivers at a different speed: both ends of the two modules have to match and the form factor needs to match as well. Additionally, port speed needs to be equal or greater than the optic used.

4. Q: What does the breakout mode of 100G QSFP28 cable mean?

A: Breakout mode refers to running a 100G port as 4 separate channels of 25G or 2 separate channels of 50G. When breaking out a single 100G port to 4x 25G or 2x 50G links, the Forward Error Correction (FEC) mode on both ends of the link must be the same to ensure link-up.

Q: Can customers use third-party 100G QSFP28 Cable?

A: Yes, third-party 100G passive copper cables can be used but all the cables are required to comply with the associated IEEE specifications, as well as SFF-8636 management interface / EEPROM specifications to allow them to be correctly identified and recognized by the switch/router.