Computer Network Cabling

The majority of computer networks today use some type of cable to connect the computer systems and hardware that make up a network. Most cables used in computer networks can be categorized into three groups: coaxial, twisted pair, and fiber optic.

Coaxial: Coaxial cable, commonly referred to as coax contains a central conductor wire which is surrounded by insulating material, which is then surrounded by a braided metal shield, the final layer is the outside plastic jacket of the cable. The central wire and the braided metal shield share the same axis (center line); this is where the name "Coaxial" comes from. Coax is effective at shielding data from Electro-Magnetic Interference (EMI), and is commonly used to enable a cable modem to connect to an Internet Service Provider (ISP). In the past a BNC Connecter was found on the end of most coax cables, nowadays an F-type Connector is the norm. The cable modem is then connected to a computer system with an RG-6 Connector which meets the industry standard resistance rating of 75 Ohms.

Twisted Pair: The most common type of cabling used in computer networks is known as twisted pair and refers to twisted pairs of cables bundled together into a common jacket. Twisted pair cable consists of multiple pairs of wires twisted around each other at specific intervals and comes in two forms: shielded twisted pair (STP) and unshielded twisted pair (UTP). STP consists of twisted pairs of wires surrounded by shielding which protects the wires from EMI. STP is rare in computer networks because there is little need for shielding from EMI unless the cable is running through a location with high electronic noise. UTP is the more common cable found in computer networks because it is less expensive than STP and works efficiently enough, unless located in an area with high electronic noise as the jacket on UTP cable does not provide protection from EMI. There are many variations of UTP cable related to the number of twists per foot which determine how quickly data can propagate on the cable. The speed of the UTP cable is measured in megahertz (MHz) and different variations of UTP are given a category (CAT) rating. Current industry standards require CAT 5e which has a maximum frequency of 100 MHz and maximum bandwidth of 1000 Mbps, or CAT 6 which has a maximum frequency of 250 MHz and maximum bandwidth of 10000 Mbps. The latest upgrade to UTP cable is CAT 6a which runs at a maximum frequency of 500 MHz and 10 Gbps maximum bandwidth. Several organizations set the standards for network cabling including the International Organization for Standardization (ISO), and the Telecommunications Industry Association and Electronic Industries Alliance (TIA/EIA). UTP cable uses either RJ-11 or RJ-45 connectors for modem and computer system connections.

Fiber-Optic: Fiber-optic cable transmits data via waves of light through glass as opposed to electrical current through copper wire. The four components of a fiber-optic cable are: the core, which is the glass fiber itself, the cladding, which makes the light reflect through the fiber, the buffer, which provides support to the fragile core and cladding, and the insulating jacket. The main advantages of fiber-optic over twisted pair is speed and distance. Fiber-optic cable can transmit data for tens of kilometers as opposed to a few hundred meters with twisted pair cable. Most fiber-optic networks use Light Emitting Diodes (LED) and are known as multimode, some others use lasers and are known as singlemode, however singlemode fiber-optics often suffer from a problem known as modal distortion. Fiber-optic cables require two connectors, one for sending and one for receiving data and are commonly known by their initials ST, SC, and LC fiber-optic connectors. While fiber-optic cable has distinctive speed and distance advantages over twisted pair, it's implementation has been hindered by cost and durability issues that are inherent with fiber-optics.

Other Cable Types: UTP and Fiber-Optic are by far the most commonly used cables in computer networks, however smaller networks can also send and receive data among computer systems via classic serial, parallel, and FireWire cables. However, Microsoft has removed the ability to network with FireWire as of Windows Vista,