Choosing Between 400G DAC, AOC, ACC, and AEC: A Simple Guide

As the demand for big data, cloud computing, and high-performance computing continues to grow from businesses and consumers, data centers are evolving towards higher speeds and larger bandwidth.

In the context of 400G connectivity solutions, the use of appropriate high-speed cables is of paramount importance. This article will provide a brief overview of how to choose among the four 400G high-speed cables: DAC, AOC, ACC, and AEC.

What Are 400G DAC, AOC, ACC, and AEC?

400G DAC Cable

400G Direct Attached Cable (DAC) mainly refers to passive direct attach cables, which use conductive copper wires for a direct connection between two ends. The internal structure of DAC typically involves a shielded Twinax design and does not include active components. DAC copper cables are primarily utilized for intra-system rack connections, linking compute servers to storage subsystems, with a maximum length of 3 meters.

400G AOC Cable

400G Active Optical Cable (AOC) utilizes optical fiber as the transmission medium, converting electrical signals into optical signals. Since the fiber core of AOC is made of insulating material, it is less susceptible to interference from electromagnetic, lightning, or radio signals during data transmission. The maximum transmission distance for 400G AOC can reach up to 100 meters.

400G ACC Cable

400G Active Copper Cable (ACC) refers to active copper cable, whose connection medium is the same as that of DAC. However, an active signal driver or equalizer chip is added inside the cable. These active chips can compensate for part of the loss caused by copper transmission, so they can transmit 2 to 3 times farther than DAC.

400G AEC Cable

400G Active Electrical Cable (AEC) is a specific type of active DAC. It contains a silicon chip inside the cable assembly, reconditioning the critical high-speed signals. The re-timers can clean, remove noise, and amplify the signal at the beginning and end of the transfer, ensuring high-speed transmission over longer distances.

What Are the Differences Between 400G DAC, AOC, ACC and AEC?

Type

• 400G DAC mainly includes two types of packaging: 400G QSFP-DD and QSFP112. For example, 400G QSFP112 Passive DAC and 400G QSFP-DD to 2x200G QSFP56 Passive Breakout DAC.

• 400G AOC mainly includes, for example, QSFP-DD to QSFP-DD AOC and 400G QSFP-DD to 4 x 100G QSFP28 Breakout AOC.

• 400G AEC and ACC mainly come in two types: direct connection and breakout cable. For example, 400G QSFP-DD to 4 x 100G QSFP28 Breakout AEC and 400G QSFP-DD ACC.

Transmission Distance

The 400G DAC and 400G AOC are both cost-effective solutions for intra-rack or adjacent rack interconnects, with their transmission distances influenced by the transmission medium.

• 1. The 400G DAC utilizes copper cables as the transmission medium, thus having a standard transmission distance typically limited to around 3 meters.

• 2. 400G AOC utilizes optical fibers as the transmission medium, with a maximum transmission distance of up to 100 meters.

• 3. Furthermore, the 400G ACC and 400G DAC share the same transmission medium, using copper cables. However, due to the inclusion of electronic components, the transmission length of 400G ACC is relatively longer by 2-3 meters compared to 400G DAC.

• 4. The transmission distance of 400G AEC primarily ranges from 3 to 7 meters.

Power Consumption

• 1. In terms of power consumption, it is evident that 400G DAC has a significant advantage with a power consumption of less than 0.1W, making it an energy-efficient choice.

• 2. 400G ACC cables, in contrast to 400G DAC cables, experience increased power consumption and costs. The performance of 400G ACC cables is heavily dependent on the internal active chips, where the bandwidth, gain, and equalization capabilities of these chips play a crucial role. Within 400G ACC cables, active chips mainly come in two types: Redriver and Retimer.Redriver is an analog chip primarily used for signal equalization and amplification, enhancing only the signal or high-frequency components. However, this may lead to the accumulation of jitter and noise. In contrast, Retimer restores the clock, resamples the signal, and sends it out, contributing to better signal improvement. Nevertheless, Retimer usually comes with higher prices and power consumption.

• 3. The power consumption of 400G AOC is approximately 10W.

• 4. 400G AEC, as a reliable plug-and-play alternative to 400G AOC, can be employed in high-speed interconnect scenarios of up to 400Gbps. However, its power consumption is only half that of 400G AOC, coupled with lower costs.

Cost

Due to the generally higher cost of optical fibers compared to copper cables, the price of 400G AOC is typically higher than that of 400G DAC (assuming similar levels or packaging). The cost of 400G AEC falls between 400G DAC and 400G AOC. The cost of 400G ACC is higher than that of 400G passive DAC due to the presence of active chips internally.

Application

• 1. 400G DAC are primarily used within system racks, connecting compute servers to storage subsystems within a maximum length of 3 meters.

• 2. 400G AOC finds widespread application in data centers for high-speed and short-distance connections. Utilizing optical fiber transmission, 400G AOC offers characteristics such as lightweight, long transmission distances, easy wiring, and insensitivity to electromagnetic radiation.

• 3. In contrast, 400G AEC provides a longer transmission distance compared to 400G DAC, offering a lower-cost and lower-power solution for intra-rack and inter-rack scenarios compared to 400G AOC.

• 4. 400G Active copper cables are commonly deployed in data centers and high-performance computing environments, linking network devices, servers, storage equipment, and other network components. They provide an economical and efficient solution for mid-range to short-distance data transmission, delivering reliable performance and high-speed connections.

How to Choose 400G DAC, AOC, ACC and AEC?

In the 400G high-speed connection solution, if there is a need for long-distance transmission and high performance requirements, AOC is preferred because it is easy to wire and is not susceptible to electromagnetic interference.

If customers have requirements regarding price, power consumption, etc., and do not need long-distance wiring, 400G DAC is undoubtedly the most economical choice.

Compared with 400G DAC, 400G ACC provides longer transmission distance and less transmission loss. In addition, they are more affordable and consume less power than 400G AOC.

400G AEC is more suitable for cabinet connections and distributed frame DDC. It has a smaller footprint, saving up to 70% of wiring space compared to 400G DAC. Moreover, it offers cost and power consumption advantages over 400G AOC.

Customers can choose the connection solution that best suits their needs based on their specific needs, weighing factors such as transmission distance, power consumption, cost, application scenarios, etc.