{"id":101664,"date":"2026-09-01T13:36:15","date_gmt":"2026-09-01T13:36:15","guid":{"rendered":"https:\/\/optics.carritech.com\/?p=101664"},"modified":"2026-09-01T13:36:16","modified_gmt":"2026-09-01T13:36:16","slug":"dac-vs-aoc","status":"publish","type":"post","link":"https:\/\/optics.carritech.com\/pt\/dac-vs-aoc\/","title":{"rendered":"DAC vs AOC: which one should you actually buy?"},"content":{"rendered":"

If you need to connect two switches, you have three options: a copper DAC, an optical AOC, or transceivers with fibre between them. All three carry the same traffic. They cost very different amounts.<\/p>\n\n\n\n

Here is how to choose, without the jargon.<\/p>\n\n\n\n

The short answer<\/h1>\n\n\n\n
Distance<\/strong><\/td>What to use<\/strong><\/td><\/tr><\/thead>
Under 3 metres, same rack<\/td>Passive DAC<\/strong> \u2014 cheapest, lowest power<\/td><\/tr>
3\u201315 metres, next rack along<\/td>Active DAC or AOC<\/strong><\/td><\/tr>
15\u2013100 metres, same row or hall<\/td>AOC<\/strong><\/td><\/tr>
Over 100 metres<\/td>Transceivers and fibre<\/strong><\/td><\/tr>
Any link through a patch panel<\/td>Transceivers and fibre<\/strong><\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n

That last row catches people out, so it is worth saying plainly: a DAC and an AOC are single, fixed cables.<\/strong> They plug straight from one switch port into another. If your link runs into a patch panel, you cannot use either one, no matter how short the run is.<\/p>\n\n\n\n

DAC: the cheapest link you can build<\/h1>\n\n\n\n

A Direct Attach Cable is copper with transceiver-shaped ends moulded on. There is no laser and no optics inside \u2014 just wire. That makes it the cheapest option by a wide margin, and it draws almost no power, around a tenth of a watt.<\/p>\n\n\n\n

Best for:<\/strong> server to top-of-rack switch, and switch to switch inside the same cabinet.<\/p>\n\n\n\n

One thing to watch: DAC reach shrinks as speed goes up. At 10G and 25G you can expect around 5 metres. At 400G and 800G, expect 2 to 3 metres. Always check the length against the speed you are buying, not against a general figure.<\/p>\n\n\n\n

The trade-off is bulk. A 400G DAC is thick and stiff. Forty of them behind one switch will restrict airflow and make the cabinet hard to work in.<\/p>\n\n\n\n

Carritech stocks DAC across the full speed range:<\/strong> 10G SFP+<\/a> \u00b7 25G SFP28<\/a> \u00b7 40G QSFP+<\/a> \u00b7 100G QSFP28<\/a> \u00b7 200G QSFP-DD<\/a> \u00b7 400G QSFP-DD<\/a> \u00b7 800G OSFP<\/a><\/p>\n\n\n\n

All tested for compatibility with major switch vendors and shipped from UK and EU stock. Browse the DAC range \u2192<\/a><\/p>\n\n\n\n

AOC: when you need more than a few metres<\/h1>\n\n\n\n

An Active Optical Cable is two transceivers with fibre permanently joined between them. Your switch still sees a simple cable, but the signal travels as light instead of electricity.<\/p>\n\n\n\n

That gets you three things a DAC cannot offer:<\/p>\n\n\n\n