Cat6A vs. Fibre Decision Guide
Most security projects mix both media. Copper feeds the edge devices. Fibre carries the backbone. The skill is knowing where the line sits. This guide covers the trade-offs and ends with a decision table you can hand to a designer.
The 100 m channel limit
Balanced twisted-pair cabling is held to a 100 m channel under ANSI/TIA-568 and CSA T528. That figure is 90 m of horizontal cable plus 10 m of patch cords and equipment cords combined. It is a hard limit, not a guideline. Run past it and you lose the warranty, the test pass, and often the link itself.
Fibre has no such constraint at the scale of a building. OM4 multimode supports 10 Gb/s well past 300 m. OS2 singlemode runs kilometres. When a camera sits more than about 90 m of cable route from the nearest telecom room, copper is out and you plan a fibre run or an intermediate space.
Copper: Cat6 and Cat6A
Cat6 supports 10GBASE-T only to roughly 55 m, and only when alien crosstalk is controlled. For anything you expect to live past one refresh cycle, Cat6A is the safer specification. It carries 10 Gb/s to the full 100 m.
PoE heat is the other reason to favour Cat6A. High-wattage PoE (Type 3 and Type 4, up to 90 W at the port) heats the cable bundle. Heat raises insertion loss. Cat6A has a larger conductor and better thermal behaviour, which matters in a filled conduit or a tightly packed bundle. The TIA TSB-184-A guidance on PoE bundle sizing assumes you are managing this, and Cat6A gives you margin.
Fibre: OM4 and OS2
OM4 is a high-bandwidth multimode fiber, good for in-building backbone and 10G to 40G over the distances a campus needs. OS2 singlemode costs a little more in optics but removes distance worry entirely, and it future-proofs for higher speeds. For a new entrance facility or inter-building run, OS2 is the default. For a riser between floors, OM4 is usually enough and the optics are cheaper.
Cost, simply put
Copper cable and connectors are cheaper, and copper carries PoE, which fibre cannot. That is the deciding factor for cameras: a PoE camera on copper needs one cable. The same camera on fibre needs a media converter and local power, which adds cost and a failure point. So you push copper as far as the 100 m rule allows, then switch to fibre.
Decision table
| Scenario | Recommended media | Why |
|---|---|---|
| PoE camera within 90 m of cable route | Cat6A | One cable for data and power, full 10G headroom |
| PoE camera in a hot bundle or conduit | Cat6A | Better thermal margin under Type 3/4 PoE |
| Camera beyond 100 m channel | OS2 fibre plus local power or PoE injector | Distance exceeds copper limit |
| Riser backbone between floors | OM4 | High bandwidth, lower optic cost than singlemode |
| Inter-building or entrance facility | OS2 | Long distance, future speed upgrades |
| Short uplink, switch to switch in one room | Cat6A or DAC | Cheapest reliable option at short range |
Practical summary
Default to Cat6A for the horizontal and for PoE devices. Default to fibre for backbone and anything past the channel limit. Use OS2 where distance or longevity is in question, OM4 where it is a short riser. Test every link to the category you specified, and keep the report.
References
Last updated 2026-06-14.