Cat6, Cat6A or fibre: which cable does your office need?

What the categories actually mean

Cat5e, Cat6 and Cat6A are copper data cables built to different standards. Each step up uses tighter twists, better separation between the wire pairs and sometimes shielding, so the cable can carry faster signals with less interference. All three use the same familiar plug, which is why people often assume they are interchangeable. They are compatible, but they are not equal, and the cable is the one part of a network you cannot cheaply upgrade once it is buried in walls and ceilings.

Cat5e handles one gigabit comfortably and still exists in plenty of older buildings. Cat6 also runs one gigabit over the full 100 metres and can reach ten gigabits over short runs. Cat6A carries ten gigabits over the full 100 metres, which matters as switches, servers and access points get faster. Fibre uses light rather than electricity and works on a completely different principle.

Where Cat6 is the right answer

Desk outlets for computers, phones and printers rarely need more than one gigabit. Most laptops still have a one gigabit port, if they have a port at all, and almost no office application can saturate it. For a small office fit-out with a modest budget, Cat6 installed and tested properly will serve desks well for many years, and it is slightly thinner and easier to work with than Cat6A.

Cat6 is also a sensible choice in leased premises where you expect to move in five years and do not want to over-invest in a building you do not own. The key is quality installation: correct termination, no tight bends or kinks, and a test report for every run. A badly installed Cat6A cable will perform worse than a well-installed Cat6 one.

Why Cat6A is worth considering

Newer Wi-Fi access points can push more than one gigabit of traffic and some come with faster network ports, often 2.5 or 5 gigabits. Cat6 can usually carry those speeds over typical office distances, but Cat6A gives you the margin to go further, and it handles the heat of higher-powered PoE better when many cables are bundled together.

Cat6A costs more per metre, is thicker and stiffer, and takes more space in cable trays and wall cavities. A common compromise is Cat6 to the desks and Cat6A to ceiling locations for access points, cameras and anything else likely to need more speed or power in the future. That puts the extra spend where it is most likely to pay off.

Where fibre belongs

Copper data runs are limited to about 100 metres. Fibre goes much further, from hundreds of metres to kilometres depending on the type, so it is the standard choice for linking comms cabinets on different floors, connecting buildings across a site, and running the backbone in a large warehouse. Because it carries light, it is unaffected by electrical noise from machinery, lift motors or heavy power cables running alongside.

Fibre is also the only sensible way to link two buildings with separate power supplies. A copper cable between buildings can carry electrical surges and earth differences that damage equipment at both ends, while fibre is electrically isolated. For links between buildings, outdoor-rated fibre in a suitable duct is the normal approach.

Single-mode versus multimode

There are two main families of fibre. Multimode is typically used for shorter runs inside a building, such as between floors, and was traditionally cheaper to connect. Single-mode handles much longer distances and higher speeds, and is what the fibre company uses to bring your internet connection to the building.

The price gap between the two has narrowed over the years, and many installers now recommend single-mode even for internal backbones because it gives the most headroom. Whatever is chosen, the switches at each end need matching modules, so record the fibre type and connector style in your documentation. Mismatched modules are a common reason a new fibre link does not come up.

Questions to ask your installer

Ask what category they propose for desks, ceilings and backbone links, and why. Ask whether every run will be certified with a proper tester and whether you will receive the report. Ask how they will label outlets and patch panel ports, and whether cable routes avoid power cables and fluorescent light fittings. Any work on power circuits, new power points or switchboards is for a registered electrician, not the data cabling team.

Finally, ask for spare capacity. Adding two extra cables to each location during an install costs very little compared with coming back later to pull new ones through a finished ceiling, especially in an occupied office where every ceiling tile lifted disturbs someone. Ask also how long the installer keeps your test results on file, in case your own copy goes missing.