DAC Cables vs AOC Cables

DAC Cables and AOC Cables are widely applied in data centers for high-performance computing network cabling system owing to their lower latency,  lower power and lower cost. 
Direct Attach Cable (DAC) is comprised of a twinax copper cable, DAC cables can be classified into twofold: passive DAC & active DAC. Both passive and active DAC cables can transmit electrical signals directly over copper cable. The former can deliver without signal conditioning, while the latter has electric components inside the transceivers to boost signals. Normally speaking, DAC cabless are used to connect switches, servers, and storage inside racks.
Active Optical Cable (AOC) consists of a multimode fiber optic cable terminated with SFP form factor connectors on both ends, which requires external power to complete the conversion of electric and optical signals, from the electric signals to optical ones, and then convert to electric signals finally. Generally speaking, AOC cables are mostly used to link switches, servers, and storage between different racks inside data centers.

Comparison of DAC and AOC

Power Consumption: the operating expenses on power consumption will be decreased when adopting the DAC options.

Transmission Distance: DAC cabling solutions are suitable for short-range transmissions, while AOC solutions are applied in long-range networking cases.

Cost:When implemented in large-scale data centers, the sum of money will be saved for large quantities of DAC cables compared to AOC options.but for long-range applications,AOC cable will be cheaper

EMI Immunity: AOC cables are immune to electromagnetic interference, which can be used in most situations


Application of AOC and DAC

DAC Cable Typical Application

The major utilization of 10G SFP+ DACs is connecting switches/servers to switches within or adjacent to the rack. In other words, these 10G direct attach cables can be used as an alternative for ToR (Top of Rack) interconnections between 10G ToR switch and server or the stacking of 10GbE switches. Since 10G SFP+DAC typically supports a link length of 7 m with low power consumption, low latency and low cost, this option is an ideal choice for this short-range server-to-switch connections.


10G SFP+ AOC Cable Typical Application

Without the strict link length limits, 10G SFP+ AOCs are commonly used in several locations in the data center like ToR, EoR (End of Row) and MoR (Middle of Row). Like the DACs, the servers all connect up to a Top of Rack Ethernet switch, and each of them will have one or two Ethernet connections up to the switch and these can be patched by using AOC cables.
What's more, the utilization of 10G AOCs in the data center can also be realized in several main networking areas like Spine, Leaf or Core switching areas. The interconnections are typically fulfilled by adopting these 10G SFP+ AOCs with their theoretical maximum reach being 100 m.