In-Depth Analysis of QSFP-DD 400G DAC Cables

QSFP-DD is a popular form factor in 400G data centers, where QSFP-DD 400G DAC cable is an efficient and and economical solution. This article will introduce the 400G QSFP-DD DAC Twinax Cable and the differences between the three 400G data center solutions: 400G DAC vs. 400G AOC vs. 400G transceiver with fiber optic cables.

        

400G QSFP-DD DAC Twinax Cable Introduction

       

What is a Double Density QSFP DAC?

         

The Double-density QSFP 400G DAC is fully compliant with the QSFP-DD Multi-Source Agreement (MSA). It features two 400G QSFP-DD connectors and one passive copper cable, providing 400G data rates. QDD DAC is a cost-effective alternative solution to 400G fiber optic products, quite suitable for short-range 400G Ethernet applications. 

         

                 

Double Density QSFP Direct Attach Copper Cable Features

       

The 400G QSFP-DD DAC (Direct Attach Copper) cable has the following key features:

          

High bandwidth capability: Supports data transfer rates up to 400Gbps for network applications with large bandwidth requirements.

               

Compact design: The high port density design saves rack space and improves space utilization, making it suitable for high-density installation environments.

             

Low power consumption: The power consumption of the passive 400G DAC Twinax cable can be <0.1W, with low power consumption, reducing energy consumption.

             

Low Latency: The cables are constructed through a direct-connect design and passive copper, which reduces intermediate devices and conversion processes, thereby significantly reducing signal transmission latency.

         

Benefits and Limitations of Using Passive 400G DAC Cable

         

400G Passive DAC Benefits

      

Enhance the performance of data-intensive applications: QSFP-DD DAC supports data transfer rates up to 400Gbps, which can enable faster data access, processing and transmission, improving overall network efficiency.

         

Reduce costs: Compared to fiber optic solutions, 400G DAC cables have significant cost advantages in short-distance transmission applications. DAC has lower production costs, low maintenance costs, and low power consumption, especially in data centers or enterprise networks. 

          

Rapid deployment and simplified maintenance: The 400G QSFP-DD DAC cable does not require complex configuration during installation. Users can easily connect it to a switch or server for plug-and-play and rapid deployment. This ease-of-use feature not only reduces installation time but also makes subsequent maintenance work more efficient and easier. 

           

400G Passive DAC Limitations

      

Short transmission distance: One of the biggest limitations of a passive 400G DAC is its transmission distance. Since copper cable is used as the medium, the signal will be affected by attenuation during transmission, resulting in a shorter effective transmission distance. Generally speaking, the transmission distance of 400G DAC Twinax cable is usually only 3 meters, which is not suitable for some applications that require long-distance transmission.

        

Vulnerable to EMI: Another disadvantage of copper cables is their susceptibility to electromagnetic interference (EMI). When the QSFP-DD DAC transmits signals, it will be interfered by external electromagnetic fields and the signal will be attenuated.

     

Heavy and relatively bulky: Passive QDD DACs are typically larger and heavier than other fiber optic solutions. This can become a problem in environments that require high-density cabling, especially when a large number of connections need to be laid out between servers and switches. Excessive copper cabling can affect the efficiency of equipment cabling and space utilization between equipment.

          

400G Direct Attach Cable Applications

        

Interconnection of Data Center

      

With low latency and high bandwidth characteristics, 400G DAC can provide high-speed and stable interconnection connections between different data center switches and servers. By using 400G DAC, data centers can better meet the needs of large-scale data transmission, improve network throughput and processing speed, while reducing energy consumption and costs, especially in short-distance transmission application scenarios, which has unparalleled advantages .

          

High-performance Computing (HPC)

            

High-performance Computing (HPC) is a key technology for complex scientific calculations and big data analytics. Passive Double-density QSFP 400G DACs are widely used in HPC clusters, especially for tasks that require high-capacity data transfers and low-latency response. 400G DACs provide higher bandwidth to help improve computational efficiency and performance, supporting more efficient data processing and real-time analytics.

           

Telecommunications and Networking

              

In the telecommunications industry, Double-density QSFP 400G DAC can be used to build ultra-high-speed network backbone structures. With the promotion of 5G and future 6G networks, telecom operators need to deploy higher bandwidth connectivity solutions in their core networks. Whether it is the link connection between data centers or the core interconnection of the operator's network, QDD DAC Twinax cable can provide the required stability and efficiency.

        

Cloud Computing

         

400G Twinax cable can provide the high-speed transmission required for cloud computing platforms, especially in the interconnection between cross-regional data centers. It can realize high-speed data exchange and meet the needs of real-time data processing and large-scale storage. In addition, QSFP-DD DAC can also effectively reduce latency and improve the response speed of cloud applications, ensuring that the cloud platform can provide services to global users stably and efficiently.

400G QDD Copper Cables vs. Other 400G Data Center Solutions 

           

400G QDD AOC 

             

QDD 400G AOC uses QSFP-DD form factor modules at both ends and optical fiber as the transmission medium. It can be used in 400G Ethernet with a transmission distance of 1m to 100m. It contains 4 transmit and 4 receive channels, for a total of 8 channels. Each channel's transmission rate is 50Gbps, and the total transmission rate is 400Gbps.

             

400G QDD Transceiver with Fiber Optic Cables 

                

Both Double-density QSFP 400G DAC Twinax cable and AOC are cost-effective solutions for data centers. However, when the transmission distance is greater than 100 meters, using 400G optical modules and matching optical fiber cables  (MTP/MTO/LC) is the best solution. Currently, common QDD optical modules include QSFP-DD SR8, QSFP-DD DR4, QSFP-DD XDR4, QSFP-DD LR4, QSFP-DD FR4, etc., which can meet different application environments and distances.

             

              

400G AOC vs. 400G DAC vs. 400G Optical Modules with Fiber Cables

             

The table below details the differences between the three 400G data center solutions：