Most commercial fit-outs need both copper and fibre — the question is where each belongs, not which one “wins”. Getting the split wrong either wastes containment space and budget, or leaves the building under-capacity before the tenant moves in.
The simple rule
| Layer | Typical medium | Why |
|---|---|---|
| Desk / AP / device | Copper (Cat6A) | Cost-effective, standardised, easy to patch |
| Floor distributor → building core | Fibre (OM4 or OS2) | Distance, bandwidth headroom, no alien crosstalk |
| Building → building / campus | Fibre (OS2) | Long distance, single-mode economics |
Copper carries Ethernet to the edge. Fibre carries aggregation and backbone traffic. A well-designed building uses each where it performs best.
When copper is the right call
Specify Cat6A horizontal cabling when:
- Channel length is within the 100-metre limit (including patch cords)
- End devices are 1GbE or 2.5/5/10GbE at the desk or AP
- Containment routes are already sized for copper bundles
- The client wants standardised patching without fusion splicing at the floor
Cat6A remains the default for UK office fit-outs where 10GbE readiness is required without ripping out cable in five years. See our guide on what Cat6A is and when to specify it.
When fibre is essential
Specify fibre optic backbone when:
- Distance between cabinets exceeds reliable copper limits
- You need 40G/100G aggregation between floors or buildings
- The route passes through high EMI environments (industrial, plant rooms)
- Multiple buildings share a campus network
OM4 multi-mode suits most intra-building backbones. OS2 single-mode is standard for inter-building links and long risers.
Common specification mistakes
All-copper backbone on a tall building — attenuation and bandwidth limits bite above a few floors. Fibre risers cost more upfront but avoid a mid-lease backbone rip-out.
Fibre to every desk — rarely justified in standard office fit-outs. Copper patching is cheaper to moves-adds-changes (MACs) and your client’s IT team already stocks copper patch leads.
Undersized containment for Cat6A — Cat6A has a larger outside diameter than Cat6. If the consultant specifies Cat6A, check basket tray and trunking fill early.
Testing and handover — both media
Whether copper or fibre, handover should include certified test results:
- Copper: Fluke DSX to ISO/IEC 11801
- Fibre: OTDR traces and insertion-loss results per pair
Documentation should match outlet IDs and port schedules — not a USB stick of unlabelled PDFs.
Working with AYT Infrastructure
We install and certify structured data cabling and fibre optic networks across the UK — backbone, risers and horizontal cabling with full documentation.
For specification support or a quote on your next programme, contact our team or explore our projects for representative outcomes.
Further reading: OTDR testing explained · Data cabling installation Manchester · North West logistics hub case study.