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In the 200G network architecture, DAC (optical DAC cable) and AOC (active fiber cable) are the two most commonly used interconnection solutions within the data center. Although they can all achieve 200G transmission, there are significant differences in physical characteristics, cost, and application scenarios.
| Feature | 200G DAC (Direct Attach Cable) | 200G AOC (Active Optical Cable) |
| Medium | Copper wire (electrical signal) | Fiber optic cable (optical signal) |
| Typical distance | <3 meters (usually 0.5m, 1m, 2m, 3m) | 3-30 meters (customizable up to 100m) |
| Power consumption | Almost zero (no active components) | Higher (approximately 2.5W-5W per end) |
| Delay | Extremely low (no photoelectric conversion) | Slightly high (with photoelectric conversion process) |
| Flexibility/Weight | Heavy, hard, and with a large bending radius | Lightweight, soft, and easy to wire |
| Anti-interference | Vulnerable to electromagnetic interference (EMI) | Immune electromagnetic interference |
| Cost | Extremely low (the most economical option) | Higher (about 3-5 times that of DAC) |
Application scenario of 200G DAC cable: Intra-rack
200G DAC cable is mainly used for “short, flat, and fast” connections due to its short transmission distance and thick cables.
- ToR switch to server: In a standard 42U cabinet, the switch is located at the top of rack (ToR) and the server is located below. A 1-3 meter 200G DAC cable is a standard configuration for connecting server network cards (NICs) to switches.
- Low power consumption demand scenario: For data centers with thousands of servers, the low-power feature of 200G QSFO56 Ethernet DAC cable can save significant heat dissipation and power costs.
- Fast trading/high-performance computing: Due to the lack of photoelectric conversion, the delay provided by DAC 200Gb is at the physical limit level, making it very suitable for high-frequency trading (HFT) or ultra-high performance computing clusters.
Application scenario of 200G QSFP DD AOC cable: Inter-rack
200G QSFP DD AOC fiber cable utilizes the lightweight and anti-interference characteristics of optical fibers to solve the problem of DAC not being able to reach or penetrate.
- Interconnection of switches between cabinets (Spine Leaf): When two switches are distributed in different cabinets and the distance exceeds 3 meters, the DAC 200Gb signal attenuates too quickly and AOC fiber cable must be used.
- High density cabling environment: If the wiring on the back of the cabinet is very crowded, the thick DAC copper cable will block the air duct heat dissipation. AOC’s slender body (about 3mm diameter) is more conducive to ventilation and line management.
- End of Row: Connect the aggregation switch at the end of a row of cabinets to the central column cabinet, usually at a distance of 10-30 meters, which is the golden application range for AOC.
How to choose AOC cable DAC cable?
- DAC cable is a must within 3 meters:
Unless you have extremely strict requirements for the bending radius of cables, DAC is the cost-effective king for 200G short-range connections.
- AOC must be selected for distances over 2.5 meters:
The attenuation of o200G signals on copper cables is very severe, and DAC 200Gb over 5 meters are extremely rare and have poor stability.
- Consider maintenance costs:
200G QSFP DD DAC cable is very durable and not easily broken.
AOC fiber cable adopt fiber optic cable, and if forcefully pulled or excessively bent during wiring, it can easily cause damage to the link.
Kind Reminder:
At a speed of 200G, 200G DAC cable is highly sensitive to port return loss and crosstalk. If you are using NVIDIA Mellanox switches, it is recommended to prioritize using original or compatibility verified DAC cables to avoid packet loss.