DAC and AOC cables
A DAC (direct attach copper) cable and an AOC (active optical cable) are both pre-terminated cables with a pluggable connector on each end. A DAC carries the signal over twinaxial copper and suits short runs, usually inside a rack or to the next one. An AOC carries it over fiber with optics built into each end and suits longer runs and tighter cable pathways.
Request a QuoteDAC or AOC: which one fits
The choice usually comes down to distance, cable weight and where the cable runs. Both plug into the same SFP, QSFP and OSFP-family ports as a transceiver, so neither needs a separate patch cable or a pair of optics.
- Choose a DAC for short links such as server-to-top-of-rack or switch-to-switch inside a rack. It has no optics to power, so it draws less power and adds very little latency, and it is typically the lowest-cost way to link two ports.
- Choose an AOC when the run is longer than a copper cable can carry at your speed, when you need a thinner and lighter cable for dense bundles, or when you want fiber’s immunity to electromagnetic interference.
- Neither can be shortened or re-terminated. The length you order is the length you get, so measure the path between ports, including the vertical run and the slack at each end.
Passive and active copper
Passive DAC cables have no electronics in the connectors and are limited to the shortest reaches. As port speed rises, the reach a passive cable can support gets shorter. Active copper cables add signal conditioning in the connectors to extend reach somewhat, at the cost of a little more power.
If you are unsure which a link needs, give us the port type, speed and distance and we will recommend the right cable.
Connector types and breakout cables
DAC and AOC cables are named after the transceiver form factor on their ends, for example SFP+, SFP28, QSFP+, QSFP28, QSFP-DD and OSFP. The two ends usually match, but breakout cables split one higher-speed port into several lower-speed ones, for example one 100G QSFP28 port into four 25G SFP28 connections. Breakouts are common for connecting a high-density switch to several servers.
Match the form factor and speed to the port on each device. A 25G SFP28 port, for instance, needs a 25G-capable cable even though the cage is the same size as an SFP+.
Platform compatibility
Some switches and network cards check the cable’s coding when it is plugged in and may reject or limit cables they do not recognize. When you request a quote, tell us the switch or NIC platform (for example Cisco, Arista, Juniper or Mellanox) and the exact models on each end, so the cable is specified for that equipment.
What to include in your quote request
- Speed and form factor at each end (for example 100G QSFP28 to 100G QSFP28)
- Cable type: passive DAC, active copper or AOC, or a breakout and its split
- Length, measured along the actual cable path
- Switch and NIC platforms and models on each end
- Quantity