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Cabling

Copper cable

Some of the most obvious advantages copper

offers is that it’s less expensive than fiber cable and

much easier to terminate in the field. Because copper

is the most commonly installed cable, there is a vast

selection of connecting hardware and networking

devices, which are also less expensive than fiber

equipment.

Unshielded twisted pair (UTP).

UTP. This is the most widely used cable. Known as

balanced twisted pair, UTP consists of twisted pairs

(usually four) in a PVC or plenum jacket. When

installing UTP cable, make sure you use trained

technicians. Field terminations, bend radius, pulling

tension, and cinching can all loosen pair twists and

degrade performance. Also take note of any sources

of EMI. Choose UTP for electrically quiet environments.

Shielded twisted pair (STP, F/UTP,

S/FTP, ScTP, S/STP).

Use shielded cable to extend distances and to

minimize EMI. Sources of EMI, commonly referred to

as noise, include elevator motors, fluorescent lights,

generators, air conditioners, and printers, etc. In

10-GbE, shielded cable can also reduce ANEXT.

Shielded cable can be less balanced than UTP

cable because of the shield. The metal sheaths in

the cable need to be grounded to cancel the effect

of EMI on the conductors. Shielded cable is also more

expensive, less flexible, and can be more difficult to

install than UTP cable. Most shielded cable is thicker

than UTP, so it fills conduits quicker. Keep that in

mind as you plan your cable pathways.

STP. This is twisted pair cabling with a shield. There

are two common shields: foil sheaths and copper

braids. Foil gives a 100% shield while a copper braid

provides 85% to 95% coverage because of the holes

in the braid. But, a braided shield offers better

overall protection because it’s denser than foil and

absorbs more EMI. A braided shield also performs

better at lower frequencies. Foil, being thinner,

rejects less interference, but provides better protection

over a wider range of frequencies. For these reasons,

combination foil and braid shields are sometimes

used for the best protection. Shields can surround all

the twisted pairs and/or the individual twisted pairs.

Unshielded

twisted-pair cable (UTP)

Foiled/unshielded

twisted-pair cable (F/UTP)

Stranded conductor

Shielded/foiled

twisted-pair cable (S/FTP)

Solid conductor

Foiled/Unshielded Twisted Pair (F/UTP). Foil is the

most basic cable shield. Cables with an overall foil

shield surrounding all the pairs are called F/UTP.

These may also be called FTP cables.

Shielded Foiled Twisted Pair (S/FTP). This cable

features individual foil-shielded pairs and an outer

shield, which can be braided or foil. It offers the best

protection from external noise and ANEXT. This cable

was traditionally called Screened Twisted Pair (ScTP).

You may also see it listed as S/STP.

Solid vs. stranded conductors.

Copper cable conductors can be solid or stranded,

whether the cable is shielded or unshielded.

Solid-conductor. This cable is designed for

both backbone and horizontal cable runs. Use it for

runs between equipment rooms or from the tele-

communications room to the wallplate. Solid cable

shouldn’t be bent, flexed, or twisted. Its attenuation

is lower than that of stranded-conductor cable.

Stranded-conductor. This cable is used primarily

as a patch cable between the outlet and desktop and

between patching equipment. Stranded-conductor

cable is more flexible than solid-core cable. However,

attenuation is higher, so the total length of a

stranded cable in your channel should be kept to

10 meters or less to reduce signal degradation.

PVC vs. plenum.

PVC cable features an outer polyvinyl chloride

jacket that gives off toxic fumes when it burns. It’s

most commonly used between the wallplate and

workstation. It can be used for horizontal and vertical

runs, but only if the building features a contained

ventilation system.

Plenum cable has a special coating, such as Teflon

FEP, which doesn’t emit toxic fumes when it burns.

A plenum is a space within the building designed for

the movement of environmental air. In most office

buildings, the space above the ceiling is used for the

HVAC air return. If cable goes through that space,

it must be “plenum-rated.” LS0H (Low Smoke, Zero

Halogen) is a type of plenum cable with a thermo-

plastic compound that reduces the amount of toxic

and corrosive gases emitted during combustion.

TECH TIP

AWG —

American

Wire Gauge (AWG) is

a classification system

for the diameter of the

conducting wire. The

more a wire is drawn or

sized, the smaller the

diameter. For example, a

24-gauge wire is smaller

than an 18-gauge wire.

Foil

Braid

1 2 ... 6 7 8 9 10 11 12 13 14 15 16 ... 47 48

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