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The difference between AOC cables and DAC cables
AOC (Active Optical Cable) and DAC (Direct Attached Cable) are both used for data center short distance server interconnection and server switch interconnection. There are some key differences between the two.
Power Consumption
The maximum power consumption of AOC active cable is lower than that of DAC high-speed cable.
Transmission Distances
The maximum power consumption of AOC active cabThe transmission distance of AOC active optical cable (OM3) is generally longer compared with DAC, some up to 100m, while that of DAC high-speed cable is generally limited to approximately 7m.
le is lower than that of DAC high-speed cable.
Transmission Media
AOC active optical cable adopts optical fiber material (insulation), which belongs to optical fiber communication and is not interfered by electromagnetic wave. The DAC high-speed cable is made of copper wire, which belongs to electrical communication and will be subject to electromagnetic interference.
Transmission Signals
The transmission signal of AOC active optical cable is optical signal, while that of DAC high-speed cable is low-voltage pulse signal.
Pricing: The price of optical fiber material is generally higher than that of copper cable, primarily due to the modules at both ends of active optical cable contain lasers, while DAC high-speed cable does not.
Volume and Weight
With the same length, the weight of AOC active optical cable is about 1/4 of that of DAC high-speed cable, and its volume is about 1/2 that of DAC high-speed cable, making installation and transportation more convenient.
Transmission Performance
The bit error rate of AOC active cable is lower than that of DAC high-speed cable.
| Direct Attach Copper (DAC) | Active Optical Cable (AOC) | 2 Transceivers + Structured Cabling | |
| Reach | <15m | 100m | Per TIA/IEEE Standard |
| Cable Type | Twinax Copper | Fiber Optic | Twisted pair copper or fiber optic |
| Power Consumption | <1w | 1-2w | 1-2w |
| Weight | Heaviest Weight | Lightest Weight | Depending on structured cabling deployed |
| Bend Radius | 24AWG=38mm 26AWG=33mm 28AWG=25mm 30AWG=23mm | 25mm | Depending on structured cabling deployed |
| Application | Top of Rack(ToR) Adjacent racks | Top of Rack(ToR) Middle of Row End of ROw Zone-to-zone | Top of Rack(ToR) Middle of Row End of Row Zone-to-zone |
| EMI | Weak | Strong | Strong |
| Price | Cheapest | Less expensive than 2 Transceivers + Structured Cabling | Most expensive |
Applications of DACs and AOCs
AOC (Active Optical Cable) and DAC (Direct Attached Cable) are both used for data center short distance server interconnection and server switch interconnection. There are some key differences between the two.
DAC
DAC is for short-distance transmission.
DAC is widely used in data center switches, Large-capacity I/O storage devices, and connected with high-density network devices.
AOC
The transmission distance of AOC is longer than DAC.
AOC is used in data centers, high-performance computers, large-capacity I/O storage area networks and other equipment for high-speed and high-reliability transmission.
AOC usually meets the industrial standard of electrical interface. Through the internal electrical-optical-electrical conversion, it can exert the superiority to be used for data transmission.
How Are DACs And AOCs Used in Data Center?
25G SFP28 to SFP28 DAC can establish a 25G network through the SFP28 port of a switch. It meets IEEE P802.3by and SFF-8402 SFP28 standards and is widely used in data center network.
The transmission distance of 25G SFP28 AOC can be up to 70m with OM3 multimode fiber and can be up to 100m with OM4 multimode fiber. It is used in short-distance data center interconnection applications and provides a solution of the connection between adjacent racks.
QSFP28 port interconnects with SFP28 port
We can use 100G QSFP28 to 4*25G SFP28 DAC high-speed cable or 100G QSFP28 to 4*25G SFP28 AOC to realize the interconnection between 100G equipment and 25G equipment.
QSFP28 port interconnects with SFP+ port
If we want to interconnect the QSFP28 port with the SFP+ port, we need to reduce the speed of the QSFP28 port of the switch to 40G first. And then use 40G QSFP+ to 4*10G SFP+ DAC high-speed cable or 40G QSFP+ to 4*10G SFP+ to realize the interconnection of QSFP28 port and SFP+ port.
The solution of AOC and DAC used in QSFP28 port interconnection with QSFP+, SFP28, SFP+ port introduced. In addition to the 100G rate, the QSFP28 port of the switch can also be used at 40G, 4*25G, 4*10G run. Therefore, 100G switches can be used with 40G, 25G, and 10G rate communication equipment.
