What Are the Types of 100G QSFP28 Cables?
Updated at Dec 19th 20241 min read
From providing flawless, high-bandwidth media to real-time connectivity with customers around the world, today's data centers require ultra-high-speed data transmission, which is driving the growth of the optical communication industry. QSFP28 cables are essential for data transmission. How many types of QSFP28 cables are available on the market, and what are they? This article will explore the different types and their applications.
QSFP28 Cables Basics
The QSFP28 cable comes in two main forms: a high-speed cable with QSFP28 connectors on both ends, enabling 100Gbps data transmission over a thin twinax copper cable or fiber optic cable. The other is a breakout cable, which splits one 100G signal into 4x 25G (QSFP28 to SFP28) or 2x 50G, facilitating connectivity between network devices with different speed ports while fully optimizing port bandwidth usage. This versatility ensures enhanced network flexibility and efficiency.
Types | Data Rate | Connector Type | Cable Type |
100Gbps | QSFP28 to QSFP28 | Passive Twinax Copper Cable | |
100Gbps | QSFP28 to QSFP28 / QSFP28 to SFP28 | Passive Twinax Copper Cable | |
100Gbps | QSFP28 to QSFP28 | Optical Cable | |
100Gbps | QSFP28 to QSFP28 | OM3 |
Types of 100G Passive DAC QSFP28 Cable
There are generally two types of 100G DAC（Direct Attach Cable）: 100G Active DAC and 100G Passive DAC. Among these, 100G Passive DAC is further divided into three main categories:
100G QSFP28 to 100G QSFP28 Passive DAC
100G QSFP28 to 4x 25G SFP28 Passive DAC
100G QSFP28 to 2x 50G QSFP28 Passive DAC
100G QSFP28 to 100G QSFP28 Passive DAC
100G QSFP28 to 100G QSFP28 Passive DAC is a 4-lane passive copper cable that combines four 28Gbps data lanes into one high-density cable. It offers 4 independent data transmission channels and 4 data reception channels via copper cable, providing a cost-effective solution to establish a 100G DAC link between QSFP28 ports of switches within racks and across adjacent racks. This makes it ideal for data centers, high-end servers, and enterprise wiring closets. QSFP28 DAC cables are commonly applied for Rack (ToR) interconnections between 100G ToR switches and servers or for stacking 100GbE switches (as shown in the figure below).
Figure 1: Application of 100G QSFP28 Passive Direct Attach Cable
100G QSFP28 to 4× 25G SFP28 Passive DAC
100G QSFP28 to SFP28 Passive DAC is a breakout cable providing a hybrid transition from a QSFP28 on one end to four individual SFP28 on the other end. It offers four parallel, bi-directional channels, each operating at up to 25Gbps. Featuring low crosstalk, small bend radius, and low power consumption, the 100G to 25G breakout cable meets the ever-increasing demand for high-density QSFP28 DAC connectivity with high-level signal integrity. It is widely used in high-performance computing, top-of-rack switching, and network storage deployments.
100G QSFP28 to 2x 50G QSFP28 Passive DAC
100G QSFP28 to 2x 50G QSFP28 breakout DAC is a 4-channel parallel copper cable offering 4 independent data transmission and reception 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 100G DAC to 2x 50G Ethernet connectivity, it meets the growing needs for higher bandwidth in data centers. This QSFP28 DAC cable is suitable for Infiniband EDR and 128G Fiber Channel applications.
Figure 2: 100G DAC Breakout Cables
Types of 100G AOC QSFP28 Cable
100G AOC (Active Optical Cable) is a communication cable that uses external energy to convert electrical signals into optical signals or vice versa during the communication process. There are commonly two types of 100G AOC: 100G QSFP28 to 100G QSFP28 AOC and 100G QSFP28 to 2x 50G QSFP28 AOC.
100G QSFP28 to 100G QSFP28 AOC
100G QSFP28 to 100G QSFP28 AOC comprises multimode optical fiber and parallel optical modules. The QSFP28 transceivers at both ends provide photoelectric conversion and optical transmission functions, increasing the transmission rate and distance of the optical cable while maintaining compatibility with standard electrical interfaces. With no insertion loss or return loss, 100G AOC are mainly used for short-distance, high-speed multi-channel data communication applications in data center locations such as Top of Rack (ToR), End of Row (EoR), and Middle of Row (MoR) (as shown in the figure below).
Figure 3: Application of 100G QSFP28 AOC
100G QSFP28 to 2x 50G QSFP28 AOC
100G QSFP28 to 2x 50G QSFP28 breakout AOC is a high-bandwidth parallel 100G AOC that overcomes the limitations of traditional copper cables. It features a QSFP28 module at one end and two 50G QSFP28 modules at the other, providing a cost-effective solution for data center interconnection between devices with 100G QSFP28 ports and 50G QSFP28 ports. This cable is also ideal for High-Performance Computing (HPC) and network storage deployments, meeting the growing demand for higher bandwidth and flexible connectivity.
Figure 4: 100G AOC Breakout Cables
Differences Between 100G QSFP28 Cables and Modules
The 100G QSFP28 DAC and AOC are integrated cable assemblies with fixed connectors on both ends, designed for short-range, high-speed data communication in data centers. Unlike 100G optical modules, DACs use Twinax copper cables, and AOCs utilize multimode fiber, eliminating the need for separate fiber optic cables. This design simplifies deployment and reduces costs, making them ideal for connections within racks or between adjacent racks.
Another key difference lies in the technology used for signal transmission. Optical modules rely on costly optical lasers to convert electrical signals into light for long-distance communication, while DACs and AOCs do not require lasers, significantly lowering their cost. As a result, 100G DACs and AOCs are budget-friendly, high-speed solutions, often serving as practical alternatives to optical modules in environments with sufficient shorter transmission distances.
FS QSFP28 Cables Technical Overview
FS's 100G QSFP28 cables feature a low-power design that enhances network performance while reducing power and cooling costs. These cables offer high-speed, high-bandwidth transmission and are more cost-effective than optical modules for short-distance applications. With a small bend radius and plug-and-play functionality, they provide flexible wiring options that simplify rack-to-rack and in-rack connections. Most importantly, FS's 100G DAC/AOC products undergo rigorous validation with original equipment, ensuring seamless compatibility and outstanding performance with major brands like Cisco, Arista, and more. Through comprehensive compatibility testing and real-world scenario simulations, FS replicates the customer's network environment to deliver efficient, reliable connectivity solutions that ensure stable, continuous network performance.
In conclusion, FS offers a range of high-quality 100G QSFP28 cables and 100G QSFP28 optical modules, including DAC and AOC solutions, to meet the demands of modern data centers and network infrastructure. These cables provide reliable, cost-effective, and high-speed connectivity for various applications, ensuring optimal performance and scalability. Explore FS’s 100G cable options to enhance your network with cutting-edge technology and seamless connectivity.
FAQs About 100G DAC/AOC Cables
Q: What is the difference between 100G DAC and AOC?
A: 100G DAC uses Twinax copper cables with connectors on both ends, while 100G AOC uses multimode fiber (MMF) cables with SFP connectors. DAC cables are more cost-effective and consume less power, while AOC cables support longer transmission distances and are better suited for data center environments. For more information on the difference between DAC and AOC cables, please read Data Center Cabling Solution: DAC Cables vs AOC Cables.
Q: What is the structure of 100G AOC?
A: 100G 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.
Q: Can 100G QSFP28 cables be used for 40G?
A: Yes, 100G QSFP28 cables can support 40G speeds, but the reverse is not true. Both ends of the modules must match in terms of form factor and speed, with the port speed either matching or exceeding the speed of the optical module.
Q: What does the breakout mode of the QSFP28 cable mean?
A: Breakout mode allows a 100G port to be split into 4x25G or 2x50G channels. When using breakout mode, both ends of the connection must use the same Forward Error Correction (FEC) mode to ensure proper link operation.
Q: Can customers use third-party QSFP28 cables?
A: Yes, customers can use third-party 100G passive copper cables, as long as they meet the required IEEE and SFF-8636 standards for correct identification and recognition by switches/routers.