Cat6 vs Cat6A vs Fiber: Which Cable Goes Where

Switches and APs get replaced every 5–7 years. The cable in the walls and above the ceiling stays for 15 years or more. So the right question isn't "what's enough today?" but "what will be plugged into the end of this cable ten years from now?"

Opening up the ceiling of an occupied office to pull new cable costs many times more than the cable itself. You pay for labour, broken ceiling tiles, staff who can't work, and a landlord who may not let you drill again. Cable is the cheapest part of a network and the hardest part to fix later.

The numbers that matter

The 100 m is the whole channel: a permanent link in the wall of no more than 90 m, plus no more than 10 m of patch cord across both ends. Plenty of installers forget the patch allowance and pull a 98 m run through the wall. That link may light up, but it won't pass certification and it tends to misbehave under PoE.

Cat7 is missing from the table on purpose. The US standards body (TIA) never recognised it, and the ISO version specifies connectors that aren't RJ45. A "Cat7" cable sold with RJ45 plugs is not better than a properly installed Cat6A channel.

Cat6: the desk cable

Thin, easy to pull, sensibly priced. Plenty for PCs, IP phones, CCTV cameras and printers. A typical desk in Laos is unlikely to need more than 1 Gbps in the next ten years, and if it does, Cat6 already supports 2.5 and 5 Gbps over the full 100 m.

Most IP cameras draw 5–15 W of PoE and send well under 20 Mbps of video. Cat6 is the right fit. Paying extra for Cat6A to cameras is wasted money, except for PTZ cameras with heaters or strong infrared that use high-power PoE.

Cat6A: for access points and anywhere you want headroom

On new jobs we recommend Cat6A for every AP drop. The reasons:

• Full 10 Gbps at 100 m. Current Wi-Fi 7 APs already ship with 2.5G, 5G or 10G uplink ports
• Better alien-crosstalk performance (interference from neighbouring cables in the same bundle)
• Handles high-power PoE (802.3bt, up to 90 W at the switch) better: thicker conductors mean lower resistance and less heat build-up in large bundles

The downsides are real. Cat6 UTP is about 6 mm across; Cat6A usually measures 7 to 8.5 mm. That sounds small, but the cross-section nearly doubles, so a conduit or tray that took 40 Cat6 cables will take roughly half as many Cat6A. Minimum bend radius is about four times the cable diameter, and termination needs installers who have actually done it before. In older buildings with low ceiling voids, sometimes Cat6A simply won't fit.

UTP or shielded?

In most offices we install UTP. Shielded cable (F/UTP or S/FTP) only performs better when the shield is bonded properly end to end: jack, patch panel, rack and the building earth. Many older buildings in Laos have a weak earth or none at all. A shield that isn't grounded well behaves like an antenna and picks up more noise than UTP would. We use shielded cable in factories or next to large motors and inverters, and only after checking the earthing.

Fiber: the backbone, and anything that crosses between buildings

Use fiber beyond 100 m, for floor-to-floor uplinks, and every time you link two buildings.

That last rule matters most in Laos. Fiber doesn't conduct electricity. Copper run between buildings carries lightning surges and the potential difference between two separate earthing systems straight into your switches. In the rainy season we regularly see switch ports burned out at both ends for exactly this reason. Fiber also ignores motors, welders and inverters in factories and on mine sites.

• Multimode (OM3/OM4): inside a building, runs up to a few hundred metres. OM5 exists, but for offices and plants we see no reason to pay for it
• Single-mode (OS2): between buildings and over distance. Single-mode optics have come down a lot in price, so we often use OS2 even on short runs, so the customer only has to stock one type of spare

Outdoor runs need outdoor-rated, gel- or water-blocked loose-tube cable. If it goes underground, use armored cable or pull it through HDPE duct, because rodents chewing cable is a real problem in the provinces. On poles, use ADSS or figure-8 cable with a built-in messenger wire instead of lashing indoor fiber to a steel wire.

Worked example: three-floor office with a warehouse

Say a three-floor building has 60 desks, 12 APs, 16 indoor cameras, and a warehouse 140 m away.

1. Check distances first. Put the rack in the middle of the building and measure along the real tray route, not a straight line. The farthest outlet is 82 m, under the 90 m limit. If it weren't, that floor would need its own switch cabinet.
2. Split by cable type. 60 desks and 16 cameras on Cat6 (76 drops). 12 APs on Cat6A.
3. Estimate quantity. Average run 45 m plus 10% for service loops and waste: 76 × 45 × 1.1 ≈ 3,760 m, or 13 boxes of 305 m. Cat6A: 12 × 50 × 1.1 = 660 m, or 3 boxes.
4. Floor uplinks. With a switch on each floor, run at least 4 cores of OS2 per floor: 2 in use, 2 spare.
5. The warehouse at 140 m. Too far for copper and in another building. Use 6-core outdoor OS2 in buried duct, with SFP ports on the switch at each end.

Spare cores are cheapest on the day you pull the cable. If a core breaks later, you move a patch lead instead of digging a new trench.

Which cable goes where

PoE and heat in cable bundles

Cables carrying PoE warm up, and the ones in the middle of a large bundle get hottest. As cable temperature rises, insertion loss rises and the usable length shrinks. Above a ceiling under a metal roof in Laos, afternoon temperatures pass 45°C easily. Our simple rule: don't pack high-power PoE cables into big bundles in closed conduit, split them into smaller bundles on open tray, and use Cat6A for anything drawing more than 30 W. To add up the PoE load on a switch, use the PoE budget calculator and read PoE budget explained.

What we find on jobs we're called in to fix

CCA (copper-clad aluminium) cable sold as "Cat6" at a suspiciously low price is the problem we meet most. It fails the standard, snaps easily and heats up under PoE. Quick check: scrape a conductor. If it's silver underneath, it's CCA.

Other regulars:

• Indoor UTP run outdoors. Sun and humidity crack the jacket within a year or two
• Copper between buildings (see lightning, above)
• Cat6 jacks and patch panels on Cat6A cable. The channel only performs as well as its weakest component
• Power cables and data cables in the same tray with no divider
• Cable ties pulled so tight they dent the jacket. Use Velcro
• No labels, or labels that don't match the drawings. See network rack and labeling
• No certification after installation

How to accept a cabling job

A cable that "works" is not necessarily a cable that meets the standard. A link that comes up at 1 Gbps today may refuse to run at 2.5G when you upgrade the AP.

Copper: certification testing to the designed category with a proper certifier, not a blinking-light tester. You want wire map, length, insertion loss, NEXT and return loss.

Fiber: insertion loss with a light source and power meter, and OTDR traces for long or inter-building runs. Work out the loss budget before testing. Example: 600 m of outdoor OS2 at 0.5 dB/km = 0.3 dB, two connector pairs × 0.75 dB = 1.5 dB, two splices × 0.3 dB = 0.6 dB. The maximum acceptable loss is about 2.4 dB, and a good link measures well below that. If it's over, the usual culprits are dirty connectors or a tight bend.

Inspect every end-face with a scope and clean it before mating. Dirt is the most common cause of fiber faults, and on a mine or construction site there's dust everywhere.

Ask for a PDF report of every link, using the same label IDs as the drawings. That's what cable manufacturers ask for before honouring a system warranty. If an installer can't provide it, the job isn't finished.

What we'd do

Typical office: Cat6 to desks, Cat6A to APs, fiber for the backbone. Mines and factories: always fiber between buildings, in dust- and water-resistant enclosures with sealed connectors. Solid-copper cable from known brands available through Thai distributors, with system-warranty paperwork. More on how we design and install it on our structured cabling page.

Fitting out a new building?

Talk to us before the ceiling contractor closes up. Send the floor plans and the number of points you need, and we'll propose cable type per point, tray routes and conduit sizes while it's still cheap to get them right.