AOC is short for Active Optical Cables. Active refers to the power supply. AOC needs a power supply to drive its chip to work, to exchange optical signals and electrical signals, and transmit signals through optical fibers.

The main types of AOC are SFP+ to SFP+, SFP28 to SFP28, QSFP+ to QSFP+, QSFP+ to 4*SFP+, QSFP28 to QSFP28 and QSFP28 to 4*SFP28.

The advantages of AOC:

1. Light: Since the main part of AOC is optical cable, it is lighter than DAC.

2. Low electromagnetic interference: AOC transmits optical signals and is not easily affected by electromagnetic interference.

The disadvantages of AOC:

Higher cost: There are the photoelectric conversion modules and lasers in AOC. That is why the cost of AOC is higher than that of DAC.

Hard to repair: In AOC, the laser transmitter, laser receiver and optical fiber connector are attached together. It is hard to repair when the laser fails.

DAC is short for Direct Attach Cable. There are both active DAC and passive DAC. In the process of communication, it transmits electrical signals like twisted pair cables. Due to the lack of photoelectric conversion chip, its advantages are particularly obvious in the case of short-distance transmission.

The main types of DAC are SFP+ to SFP+, SFP28 to SFP28, QSFP+ to QSFP+, QSFP+ to 4*SFP+, QSFP28 to QSFP28 and QSFP28 to 4*SFP28.

The advantages of DAC:

1.Low power consumption: Passive DAC does not need power supply, and the power consumption of active DAC is generally controlled within 500mW. This is greatly outstanding characteristic to comparing with AOC’s power consumption of 2W or 3W.

2.Low cost: There is no photoelectric conversion unit inside the DAC and the transmission medium is copper cable, so its cost is much lower than that of AOC.

The disadvantages of DAC:

1. Short transmission distance: The transmission distance is only about 6 meters, since the attenuation of electrical signal is big. 

2. Susceptible to electromagnetic interference: DAC is susceptible to electromagnetic interference since its conductor is copper cable.

Due to the physical characteristics of the copper cable, in the long-distance deployment applications, the transmission speed and signal strength will be seriously affected by the distance. When the transmission wire is changed to be optical fiber, not only the signal quality is improved, but the transmission distance is also greatly improved. Therefore, AOC can transmit farther than DAC in transmission distance.

AOC transmits optical signals through optical fibers, and its loss of signals is very small during the transmission process, so the data can move at higher speed to longer distance over it. DAC transmits electrical signals through copper cables, limited by the physical properties of copper cables, the transmission distance over it is very short, and there are high requirements for anti-electromagnetic interference. AOC is superior to DAC in reliability, and it can be applied in some case that DAC cannot.

Comparison of manufacturing cost and maintenance cost:

The DAC has no the photoelectric conversion unit that AOC does, and the passive DAC does not consume power during operation, and even the heat generated by the active DAC is far less than that of the AOC, so its cooling requirement is lower than that of the AOC. That can greatly save the operating expenses. So DAC is better cost performance than AOC in manufacturing and post-maintenance.

Q: Like the DAC, the copper patch cord is also transmitted through the copper cable. Why did the DAC evolve into a product?

A: Normally, there is a conversion process between optical signal and electrical signal

when two devices are connected by AOC or optical module. But it doesn’t happen in DAC, because DAC transmits electrical signals between the two devices directly. The DAC has the same interface as the optical module, but compared with optical module and AOC, it has the cost advantage in the application of short-distance transmission.