The two media in a typical building
A structured cabling system following TIA-568 has a horizontal layer, from the floor distributor to each outlet, and a backbone layer, between distributors, floors and buildings. Copper twisted pair such as Cat6 dominates the horizontal layer because devices have copper ports and many need power over the same cable. Fibre dominates the backbone because it carries higher speeds over longer distances and is immune to electrical interference. Data centres push fibre further toward the rack; offices and hotels keep copper for almost every outlet.
So the comparison is rarely all-copper against all-fibre. It is a decision, link by link, about which medium is the better fit, and for a sourcing buyer it means two different product families with different standards, packing and test reports. The desk covers both in the LAN and coax line and the indoor fibre cable line.
Side by side
| Item | Cat6 U/UTP copper | Multimode fibre (OM3, OM4) | Single-mode fibre (OS2, G.652.D) |
|---|---|---|---|
| Reference construction | 4 pairs, 23 AWG solid copper (0.555 to 0.58 mm), cross filler, OD about 6.0 to 6.2 mm | 50/125 um fibres, tight-buffered indoor cable, 12-core OD about 6.0 to 6.3 mm | 125 um cladding, mode field diameter per datasheet, tight-buffered or loose tube cable |
| Bandwidth figure | Category performance per TIA-568 | OM3 EMB at least 2,000 MHz.km, OM4 at least 4,700 MHz.km at 850 nm | Distance set by the optics; attenuation per datasheet |
| Typical reach at 10 Gb/s | Limited channel length per TIA-568 | OM4: commonly quoted 400 m (IEEE 10GBASE-SR) | Kilometres, depending on the transceiver |
| Power to devices | Yes, PoE over the same cable | No | No |
| Interference | Twisted pairs reduce it; screened types add protection | Not affected by electrical interference | Not affected by electrical interference |
| Termination | Field-terminated modular connectors | Pre-terminated assemblies or fusion splicing | Pre-terminated assemblies or fusion splicing |
| Packing | 305 m box, gross about 13.5 to 14 kg | Drums, commonly 1 km or 2 km for indoor cable | Drums, 1 km to 4 km depending on type |
The figures are reference constructions from public datasheets; values vary by maker and are confirmed per datasheet for each order. The difference between fibre types is explained in single-mode vs multimode fibre.
Where copper wins
Copper wins wherever the device sits within the horizontal channel length and needs power. Access points, cameras, phones, access control and building management sensors all take Power over Ethernet, and one Cat6 cable replaces a data cable and a power supply. The conductor matters here: category cable requires solid copper conductors, and heat in a bundle of PoE cables rises with conductor resistance. Copper-clad aluminium sold as category cable is counterfeit, and its higher resistance makes PoE bundles run hotter. The reasons are covered in PoE and conductor size.
- Cost of the link: copper ports and field termination are usually cheaper per outlet than fibre optics at both ends.
- Installer skills: most electrical and data contractors terminate and test copper routinely.
- Retail and marketplace demand: 305 m boxes of Cat6 sell steadily to installers, which is why MOQs of 50 to 100 boxes per listing are common.
Where fibre wins
Fibre wins on distance, on links between buildings, and in places with heavy electrical noise or lightning exposure, because it carries no current between the two ends. A backbone between floors or a campus link between buildings is usually multimode for shorter runs inside one building and single-mode for longer or future higher-speed runs. In data centres, multimode OM4 and single-mode both carry links between racks, and the choice usually follows the transceivers the operator has standardised on.
Fibre is also smaller and lighter for the capacity it carries. A 12-core tight-buffered indoor cable of about 6 mm and roughly 33 to 41 kg/km per datasheet can serve several backbone links, while the same number of copper links would need a bundle of Cat6 cables at about 40 to 43 kg/km each. In crowded risers and older buildings with limited containment, that space saving is often the deciding argument. Where tight bends are unavoidable, bend-insensitive G.657 fibres reduce the risk of added loss at corners and in small enclosures.
For loss planning, older TIA-568 planning values are a useful starting point: cabled multimode 3.5 dB/km at 850 nm, single-mode indoor 1.0 dB/km, 0.75 dB per mated connector pair and 0.3 dB per splice. Use the cable maker's spec where it is available, and check the optics' power budget against the total. The full method is in fibre attenuation explained.
Fire rating, testing and sourcing
Both media must meet the same building fire rules. In the EU, cables permanently installed in buildings, copper or fibre, fall under the Construction Products Regulation, with the CPR class declared on the DoP. In the US, copper data cable is rated CMP, CMR, CMG/CM or CMX under NEC Article 800, and optical fibre cable OFNP or OFNR under NEC Article 770; the rating needed depends on the space, and US projects usually require listed products to satisfy the AHJ. A listing held by the partner plant for that construction is checked in the certifier's public database per order.
Testing differs. Copper is accepted on channel or permanent link tests with a certification tester, covered in Cat6 cable testing. Fibre is accepted on insertion loss per link, often with OTDR traces for longer runs, and pre-terminated assemblies come with factory loss records. Ask for both kinds of report in the contract, not after installation.
- Mark each link on the drawing as copper or fibre, with length and fire rating.
- Choose fibre type and core count for the backbone, with some spare cores.
- Fix copper category, screening and jacket rating for the horizontal layer.
- Agree packing: 305 m boxes for copper, drum lengths for fibre.
- List the test reports required before shipment.
Cat6 lead times commonly run from about 5 to 25 days and up to around a month on platform listings; fibre cable lead times follow fibre and tube scheduling. Both are confirmed in writing for each order, as described on the MOQ and lead time page. Send the link schedule through the quote form and the desk will split it across the right partner plants.