100G AOC And DAC: Performance And Application Differences

In the fields of modern data centers, high-performance computing, and high-bandwidth data transmission, 100G AOC (Active Optical Cable) and DAC (Direct Attach Copper) are two important transmission media, each carrying different technical characteristics and application scenarios. This article will analyze the differences between 100G AOC and DAC from multiple dimensions, aiming to provide readers with a comprehensive and in-depth understanding.

Technical Principle and Composition

1. 100G AOC (Active Optical Cable)

100G AOC is a high-performance data transmission cable that uses optical fiber as the transmission medium and has built-in active electronic components (such as lasers and photodetectors). Its technical principle is to transmit optical signals through optical fibers and add optical amplifiers to the optical cables to amplify and compensate the signals, thereby improving the transmission distance and quality. AOC optical cables are mainly composed of optical cable cores, optical amplifiers, optical fiber connectors, and optical cable protective sleeves. The optical cable core is composed of multiple optical fibers, and the optical amplifiers are distributed in the optical cable core to amplify and compensate the signals in real time.

2. 100G DAC (Direct-Connect Copper Cable)

100G DAC is a direct connection solution based on copper wire material, which uses a high-density twisted pair structure to achieve high-speed data transmission. DAC cables usually contain multiple differential pairs for transmitting differential signals to resist electromagnetic interference and improve signal integrity. Common 100G DAC cables include QSFP28 to QSFP28, QSFP28 to 4xSFP28 and other types to meet the connection requirements between different devices.

Performance comparison

1. Transmission distance

100G AOC: Due to the built-in optical amplifier, the transmission distance of 100G AOC is significantly better than that of DAC. Theoretically, the transmission distance of AOC can reach hundreds of meters or even further (depending on the performance of the optical amplifier and the quality of the optical cable). This makes AOC particularly suitable for scenarios requiring long-distance connections within data centers.

100G DAC: In contrast, the transmission distance of 100G DAC is shorter, generally no more than 10 meters (some products may reach longer distances, but the performance will be reduced). Therefore, DAC is more suitable for short-distance connections, such as equipment interconnection within a rack or between adjacent racks.

2. Bandwidth and transmission rate

100G AOC: AOC optical cable can support data transmission rates up to 100Gbps or higher while maintaining low signal latency. This is due to the high bandwidth and low loss characteristics of optical fiber communication, as well as the signal amplification and compensation functions of optical amplifiers.

100G DAC: DAC cable also supports 100Gbps data transmission rate, but may be affected by signal attenuation and electromagnetic interference during long-distance transmission, resulting in reduced transmission performance. Therefore, the DAC can maintain excellent transmission performance in short-distance connections.

3. Anti-interference ability

100G AOC: Optical fiber acts as an insulator and is not affected by electromagnetic interference. Therefore, 100G AOC has extremely strong anti-interference capabilities and can maintain stable transmission performance in high electromagnetic interference environments.

100G DAC: The DAC cable is made of copper wire and is easily affected by electromagnetic interference. Although the anti-interference capability can be improved to a certain extent through differential signal transmission technology, it may still be interfered with in extreme environments, resulting in a decrease in signal quality.

4. Power consumption and heat dissipation

100G AOC: Although the active electronic components (such as lasers and photodetectors) built into the AOC optical cable will increase the power consumption to a certain extent, its power consumption is still lower than that of traditional optical fiber transceivers. At the same time, the heat dissipation performance of the optical cable itself is good, which helps to reduce the overall energy consumption of the system.

100G DAC: As a passive device, DAC cable has relatively low power consumption. However, during high-speed data transmission, the copper wire material may generate a certain amount of heat, and corresponding heat dissipation measures need to be taken to ensure stable operation of the system.

5. Cost and price

100G AOC: Because AOC optical cable uses optical fiber as the transmission medium and has built-in complex active electronic components, its cost is relatively high. In addition, the prices of materials such as optical fibers and lasers are also relatively high, further pushing up the overall price of AOC.

100G DAC: In comparison, the cost of DAC cables is low. It uses copper wire as the transmission medium and does not require additional electronic components and complex processes, so the cost is relatively low. This makes the DAC more competitive in cost-sensitive application scenarios.

6. Volume and weight

100G AOC: AOC optical cable uses optical fiber as the transmission medium, and its size and weight are relatively small. This makes AOC more flexible and convenient in wiring and installation, helping to reduce data center space occupation and wiring costs.

100G DAC: Although the DAC cable also adopts a compact design, its volume and weight are still larger than AOC. This may increase the difficulty and cost of wiring to a certain extent.

Application scenarios and selection strategies

1. Application scenarios

100G AOC: Suitable for scenarios that require long-distance, high-speed data transmission within the data center. Such as long-distance connections between servers and switches, cross-rack connections, etc. In addition, AOC is also suitable for environments with high requirements for data transmission quality and large electromagnetic interference.

100G DAC: Suitable for short-distance connection scenarios within the data center. Such as interconnection between devices in a rack, short-distance connection between adjacent racks, etc. DAC occupies an important position in short-distance connections with its low cost and easy installation.

2. Selection strategy

When choosing 100G AOC or DAC, comprehensive consideration should be given to specific application scenarios and requirements. Here are some suggestions:

Transmission distance: If the transmission distance is long (more than 10 meters), it is recommended to choose 100G AOC to ensure transmission performance and quality. If the transmission distance is short (within 10 meters), you can consider using 100G DAC to reduce costs.

Anti-interference ability: If there is strong electromagnetic interference in the application scenario, it is recommended to choose 100G AOC to improve anti-interference ability and ensure the stability of data transmission.

Cost and budget: In the case of limited budget, 100G DAC can be given priority to reduce costs. However, it should be noted that while pursuing low costs, the performance and quality of data transmission must also be ensured.

Installation and maintenance: The installation and maintenance of AOC optical cables are relatively simple, but it is necessary to pay attention to the bending radius of the optical cable and avoid excessive stretching. The installation and maintenance of DAC cables are simpler and faster, and no additional power supply and cooling equipment are required.

Conclusion and outlook

To sum up, there are significant differences between 100G AOC and DAC in terms of transmission distance, bandwidth, anti-interference ability, power consumption, cost, volume and weight. When choosing, comprehensive considerations should be made based on specific application scenarios and needs to make the optimal choice. With the continuous advancement of technology and the gradual reduction of costs, 100G AOC and DAC will be widely used in more fields and promote the continued development of information technology. In the future, we can expect that these two transmission media will continue to optimize and improve their performance and expand their application scenarios to provide more efficient, reliable, and economical solutions for data centers, high-performance computing, and high-bandwidth data transmission.