On The Structural Differences Between AOC And DAC

1. Structural Differences Between AOC and DAC

2. How to Choose Between AOC and DAC?

3. How to Choose?

4. Conclusion

In high-performance computer systems, especially in data centers and high-frequency network applications, data transfer speed and signal quality are crucial. With the rapid development of technologies such as 4K and 8K video processing, virtual reality (VR), and AI training, the demand for high-speed transmission cables has grown significantly. AOC (Active Optical Cable) and DAC (Direct Attach Cable) are two common types of high-speed transmission cables, each with its unique structural and performance characteristics, which determine their suitability for different application scenarios.

1. Structural Differences Between AOC and DAC

1.1 DAC (Direct Attach Cable)

DAC, or direct attach copper cable, primarily consists of copper conductors and an outer shielding layer. Data is transmitted through electrical signals within the copper conductors. Since there are no built-in amplifiers or converters, DAC is considered a "passive" cable. Its structure is relatively simple and cost-effective, making it suitable for short-distance high-speed transmission.

Characteristics:

· Material: Copper wire

· Structure: Copper conductor + shielding layer

· Power consumption: Extremely low, virtually zero

· Transmission distance: Typically used for short distances, usually 5-10 meters

· Cost: Relatively low

1.2 AOC (Active Optical Cable)

AOC, or active optical cable, is a hybrid cable that combines optical fiber and copper wire. Its core feature is that it includes built-in electronic modules capable of converting electrical signals into optical signals for transmission. These optical signals are then transmitted over fiber optic cables and later converted back to electrical signals. This design not only enables long-distance data transmission but also maintains signal integrity during high-speed transfers, reducing attenuation.

Characteristics:

· Material: Optical fiber + copper conductor

· Structure: Built-in electronic modules + optical fiber + copper conductors + shielding layer

· Power consumption: Some power consumption, mainly for driving the electronic modules and optical conversion

· Transmission distance: Can reach tens of meters or more

· Cost: Relatively higher

2. How to Choose Between AOC and DAC?

2.1 Transmission Distance

· DAC: Since DAC lacks signal amplifiers, it is best suited for short-distance transmission. Typically, it is effective for ranges within 5-10 meters, where signal attenuation is minimal. It is ideal for short-distance data transmission between devices such as servers and switches.

· AOC: For applications requiring longer transmission distances, AOC is more suitable. It supports distances of tens of meters or even longer while maintaining signal quality during long-distance transmission, making it ideal for larger data centers or high-performance computing environments.

2.2 Bandwidth and Data Transfer Rates

· DAC: Generally, DAC supports lower bandwidths, suitable for transmissions at rates up to 100G. As transmission distance increases, signal attenuation becomes more pronounced, so DAC is best for high-frequency but short-distance applications.

· AOC: AOC can typically support much higher bandwidths and data transfer rates, such as 400G, 800G, or even higher, making it ideal for applications requiring high-speed, large-volume data transmission.

2.3 Cost and Power Consumption

· DAC: With its simpler structure and absence of complex electronic modules, DAC is lower in cost and has very low power consumption, making it a good choice for budget-sensitive applications that don’t require long-distance transmission.

· AOC: Due to the presence of optical modules and other electronic components, AOC is more expensive and has higher power consumption. However, its performance advantages in long-distance and high-bandwidth applications often justify the higher cost.

2.4 Application Scenarios

· DAC: DAC is suitable for internal data center connections, especially for short-distance communication between switches, servers, or storage devices.

· AOC: AOC is ideal for applications requiring long-distance transmission and higher data rates, such as high-performance computing clusters, large-scale data centers, and long-distance connections between racks or across buildings.

3. How to Choose?

The decision to use AOC or DAC depends on the following factors:

1. Transmission Distance: If it’s a short-distance connection (within 5-10 meters), DAC is the more appropriate choice, as it offers better cost-effectiveness and meets bandwidth needs.

2. Bandwidth Requirements: If high bandwidth or large data volume is required, and the transmission distance is long, AOC will be the better choice.

3. Budget Constraints: DAC, with its simple structure, is more cost-effective and suitable for applications with limited budgets. On the other hand, AOC is more appropriate when budget permits and higher performance is required.

4. Power Consumption: If power consumption is a key consideration, DAC’s low power consumption might be more appealing.

4. Conclusion

Both AOC and DAC have their own strengths and weaknesses. When choosing between the two, it’s important to consider the specific application requirements, including transmission distance, bandwidth needs, cost constraints, and power consumption. For most short-distance, high-speed connections, DAC may be the most cost-effective solution. However, for long-distance transmission and high-bandwidth requirements, AOC is often the better choice. By understanding the structural differences and performance characteristics of both, users can make more informed decisions to meet their specific transmission needs.