Does Structured Cabling Include Fibre? Where Copper Stops and Fibre Starts

Yes. Structured cabling normally includes both fibre and copper. The term describes an organised cabling system for a building or campus, not one type of cable. In most offices, fibre carries the backbone between floors and buildings, and copper carries the last stretch to the desks, cameras and wireless access points. What matters on a real job is where one stops and the other starts, because that line decides the cost and what the network can carry later.

The usual split in a building

Structured cabling is laid out in layers, and each layer has a natural choice of cable.

• Between buildings: singlemode fibre. It covers the distance and makes no electrical connection between the two buildings.
• Riser, between floors: fibre. It carries the combined traffic of a whole floor and leaves room to grow.
• Between comms rooms and racks: fibre, or copper on short links. The choice depends on the distance and the speed of the equipment.
• Floor distribution to the outlet: Category 6 or 6A copper. It is within reach, costs less at each end, and can carry power.

This is the usual pattern, not a rule. A small office on one floor may have no fibre inside it at all beyond the line the telco brings in. A data centre may use fibre for most of its links, as set out in what changes inside a data hall.

Where copper has to stop

A copper link has a 90-metre limit between the outlet and the patch panel. Allowing for patch cords at each end, the whole channel comes to 100 metres. Past that, the link needs a switch closer to the outlets, with fibre running back to it.

Distance is not the only reason to change over. Copper conducts electricity, so a copper run between two buildings can carry a surge or a difference in earth potential from one to the other. Fibre does not conduct, which also keeps it free of the electrical interference around power cables, motors and switchgear.

Why the desks are still on copper

If fibre carries more over a longer distance, it is fair to ask why it does not go all the way to the desk. There are three plain reasons:

• Power. Power over Ethernet sends power down the same copper cable as the data, which is how most cameras, wireless access points and desk phones are run. Fibre cannot do this.
• Equipment. Laptops, phones and printers connect by copper or wireless. A fibre outlet at a desk needs a converter or a fibre network card.
• Cost at the ends. Copper is simpler to terminate, and switch ports for it cost less.

Fibre to the desk does exist, and it can suit a site with very long runs or heavy electrical interference. For most offices, copper to the outlet remains the practical choice.

Which fibre to specify

"Fibre" on a quotation is not enough, because there are two families and they are not interchangeable on the same link.

Singlemode (OS2) carries over kilometres and is the normal choice between buildings and on long backbones. The cable is not the costly part of the system. The transceivers at each end have tended to cost more than multimode ones, although the gap depends on the equipment.

Multimode (OM3, OM4) suits shorter runs inside a building or data centre. At 10 gigabits per second, OM3 is rated to 300 metres and OM4 to 400 metres. Higher speeds reduce those distances, so check the reach against the speed the network will actually run.

If a riser could be asked to carry more in ten years, it is worth pricing singlemode as well as multimode. Fibre in a riser is much harder to replace than the equipment connected to it. Laying spare cores at the same time also costs far less than adding a second cable later.

What to check in a quotation

Copper and fibre are often priced together under one "structured cabling" line. That makes it easy for fibre to be assumed by one side and left out by the other. Before comparing prices, make sure each quotation states:

• Whether the riser and any links between comms rooms are included, and in which cable
• The fibre type and core count on every run
• How the fibre is terminated, and whether splicing, trays and patch panels are in the price
• Whether the link from the telco's termination point to your comms room is included
• The test method for fibre and for copper, and whether the readings are handed over

Two quotations for the same floor can differ widely because one includes the backbone and the other assumes it already exists. How to compare structured cabling contractors goes through the other gaps to look for, and what moves the price explains the cost side.

Test each one the right way

Copper and fibre are certified differently. Copper links are tested with a cable certifier against their category. Fibre links are tested for loss with a light source and power meter, with an OTDR added where the run or the contract calls for it. The differences are explained in OTDR vs power meter testing. Ask for the readings for both at handover, not only a line that says "pass".

Where Fiber Tech sits

Fiber Tech Solutions Pte Ltd installs copper and fibre as one job, so the backbone and the floor cabling are planned, tested and documented together. The company holds IMDA Wiring Contractor (Class) Licence No. IW105464, is FOA-certified for splicing and termination, and has cabled more than 1,000 buildings since 2007. To discuss a building or a floor, get in touch.

— Written by the team at Fiber Tech Solutions Pte Ltd, IMDA-licensed wiring contractor and FOA-certified fibre specialists, Singapore.