Data Center Cabling Solutions: Analysis Of DAC And AOC Cables

Introduction

Data center cabling system is not only a physical connection, but also a combination of data transmission, signal conversion and energy distribution. With the explosive growth of data volume and the continuous improvement of transmission rate, the requirements for cabling system are getting higher and higher. DAC cable and AOC cable are two mainstream choices in data center cabling solutions. Each has its own unique advantages and characteristics, suitable for different application scenarios and needs.

DAC cable: the best choice for short-distance transmission

1. DAC cable overview

DAC cable is a direct-connect cable with a twinax copper cable structure. Both ends are equipped with optical modules such as SFP+, SFP28, QSFP+, QSFP56 or QSFP28, which can be directly connected to switches, servers and other devices. DAC cables are divided into two types: passive DAC and active DAC. The former can realize the transmission of electrical signals without any signal conditioning, while the latter has built-in electronic components in the transceiver to amplify the signal and support longer transmission distances.

2. DAC cable advantages

Cost-effectiveness: DAC cable uses copper cable as the transmission medium, which is relatively low in cost, and has a simple internal design and fewer components, so it has high cost-effectiveness in short-distance transmission.

Low power consumption: Passive DAC cables have extremely low power consumption, usually less than 0.15 watts, while active DAC cables have much lower power consumption than AOC cables, which helps reduce energy consumption and operating costs of data centers.

High bandwidth and low latency: DAC cables can provide high bandwidth and low latency data transmission performance over short distances, and are suitable for application scenarios with high real-time requirements.

Easy to install and manage: The rigid structure of DAC cables makes them relatively simple to install and manage, without the need for complex cabling techniques and equipment support.

3. Applicable scenarios

DAC cables are mainly used to connect switches, servers, and storage devices in the same rack within a data center for short-distance data transmission and stacking. For example, 10G SFP+ DAC cables are often used to connect top-of-rack (ToR) switches and servers, or for stacking connections of 10GbE switches. Due to its low cost, stable performance, and easy installation, DAC cables occupy an important position in short-distance transmission scenarios in data centers.

AOC cable: a powerful tool for long-distance transmission

1. AOC cable overview

AOC cable is an active optical cable that uses optical fiber as a transmission medium, and is equipped with optical transceivers such as SFP+, SFP28, QSFP+, QSFP56 or QSFP28 at both ends. AOC cable relies on an external power supply to promote signal conversion, converting electrical signals into optical signals for long-distance transmission, and then converting them back into electrical signals for equipment to receive.

2. AOC cable advantages

Long-distance transmission capability: The transmission distance of AOC cable can reach 100 meters or even longer, which is suitable for long-distance connections between different racks in the data center or across computer rooms.

High bandwidth and low attenuation: As a transmission medium, optical fiber has extremely high bandwidth capacity and extremely low attenuation rate, which can maintain signal integrity and stability over long distances.

Anti-electromagnetic interference: As an insulator, optical fiber is not affected by electromagnetic interference and can stably transmit signals in a high electromagnetic interference environment.

Energy-saving and efficient: Although AOC cable requires an external power supply, its overall power consumption in long-distance transmission is lower than that of traditional copper wire solutions, which helps reduce energy consumption in data centers.

3. Applicable scenarios

AOC cables are mainly used to connect switches, servers and storage devices in different racks within the data center to achieve long-distance data transmission and networking. For example, 10G SFP+ AOC cables are widely used in multiple locations in the data center (such as ToR, EoR, MoR, etc.), which can achieve the connection between servers and top-of-rack Ethernet switches, as well as the interconnection of key network areas (such as Spine, Leaf, Core switching areas). The long-distance transmission capability and high-bandwidth characteristics of AOC cables make it the preferred solution for long-distance networking in data centers.

Comparative analysis of DAC cable and AOC cable

1. Transmission distance and bandwidth

DAC cable: The transmission distance is limited. Passive DAC cable usually does not exceed 7 meters, and active DAC cable can reach about 10 meters. In terms of bandwidth, it can support data transmission rates up to 400Gbps depending on the specific model and specifications.

AOC cable: The transmission distance can reach 100 meters or even farther; the bandwidth can also support data transmission rates up to 400Gbps, and the signal attenuation is small in long-distance transmission.

2. Power consumption and cost

DAC cable: Low power consumption, especially passive DAC cable, which has extremely low power consumption; relatively low cost, suitable for short-distance transmission scenarios.

AOC cable: Although it requires external power supply, the overall power consumption still has advantages in long-distance transmission; the cost is higher than DAC cable, but it is suitable for long-distance transmission and networking needs.

3. Installation and management

DAC cable: Rigid structure, relatively simple installation and management; but limited by the transmission distance, it is not suitable for long-distance wiring.

AOC cable: Lightweight optical fiber provides greater flexibility and is easy to install and manage; suitable for long-distance wiring needs.

4. Electromagnetic Interference

DAC cable: susceptible to electromagnetic interference, need to pay attention to the use environment.

AOC cable: optical fiber as an insulator, not affected by electromagnetic interference, suitable for high electromagnetic interference environment.

Selection strategy of data center cabling solution

In the selection of data center cabling solution, the advantages and disadvantages of DAC cable and AOC cable should be comprehensively considered according to specific needs and application scenarios. Here are some recommended selection strategies:

Clear transmission distance and bandwidth requirements: First clarify the transmission distance and bandwidth requirements within the data center to determine whether long-distance transmission and high-speed data transmission capabilities are required.

Consider cost and benefit: Choose a suitable cabling solution based on budget and long-term operating costs. DAC cable has cost advantages in short-distance transmission, while AOC cable is more cost-effective in long-distance transmission.

Evaluate electromagnetic interference environment: For high electromagnetic interference environment, AOC cable should be given priority to ensure stable signal transmission.

Consider flexibility and scalability: As the scale of data center expands and business needs grow, the cabling system should have good flexibility and scalability. AOC cable is more flexible and more suitable for future expansion needs.

Integrated cabling management and maintenance: Use a structured cabling system to manage and maintain data center cabling to ensure that the cabling is neat, orderly and easy to manage.

Conclusion and Outlook

DAC cables and AOC cables are two key components in data center cabling solutions, each with its own unique advantages and characteristics. In practical applications, appropriate cabling solutions should be selected according to specific needs and application scenarios. With the continuous development of information technology and the continuous expansion of data center scale, the complexity and importance of cabling systems will become increasingly prominent. In the future, with the continuous emergence and application of new materials and new technologies, data center cabling solutions will be more efficient, reliable and intelligent, providing strong support for the stable operation of data centers and the sustainable development of businesses.