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Cables are commonly used to carry communication signals within LAN. There are three common types of cable media that can be used to connect devices to a network and they are coaxial cable, twisted-pair cable, and fiber-optic cable.
Coaxial cable
Coaxial cable looks similar to the cable used to carry TV signal. A solid-core copper wire runs down the middle of the cable. Around that solid-core copper wire is a layer of insulation, and covering that insulation is braided wire and metal foil, which shields against electromagnetic interference. A final layer of insulation covers the braided wire.
There are two types of coaxial cabling: thinnet and thicknet. Thinnet is a flexible coaxial cable about ¼ inch thick. Thinnet is used for short-distance. Thinnet connects directly to a workstation's network adapter card using a British Naval Connector (BNC). The maximum length of thinnet is 185 meters. Thicknet coaxial is thicker cable than thinnet. Thicknet cable is about ½ inch thick and can support data transfer over longer distances than thinnet. Thicknet has a maximum cable length of 500 meters and usually is used as a backbone to connect several smaller thinnet-based networks.
The bandwidth for coaxial cable is 10 mbps (mega bits per second).
Twisted Pair Cable
Twisted-pair cable is the most common type of cabling you can see in todays LAN networks. A pair of wires forms a circuit that can transmit data. The pairs are twisted to provide protection against crosstalk, the noise generated by adjacent pairs. When a wire is carrying a current, the current creates a magnetic field around the wire. This field can interfere with signals on nearby wires. To eliminate this, pairs of wires carry signals in opposite directions, so that the two magnetic fields also occur in opposite directions and cancel each other out. This process is known as cancellation. Two Types of Twisted Pairs are Shielded Twisted Pair (STP) and Unshielded Twisted Pair (UTP).
Unshielded twisted-pair (UTP) cable is the most common networking media. Unshielded twisted-pair (UTP) consists of four pairs of thin, copper wires covered in color-coded plastic insulation that are twisted together. The wire pairs are then covered with a plastic outer jacket. The connector used on a UTP cable is called a Registered Jack 45 (RJ-45) connector. UTP cables are of small diameter and it doesn't need grounding. Since there is no shielding for UTP cabling, it relies only on the cancellation to avoid noise.
UTP cabling has different categories. Each category of UTP cabling was designed for a specific type of communication or transfer rate. The most popular categories in use today is 5, 5e and 6, which can reach transfer rates of over 1000 Mbps (1 Gbps).
The following table shows different UTP categories and corresponding transfer rate.
| UTP Category | Purpose | Transfer Rate |
| Category 1 | Voice Only | |
| Category 2 | Data | 4 Mbps |
| Category 3 | Data | 10 Mbps |
| Category 4 | Data | 16 Mbps |
| Category 5 | Data | 100 Mbps |
| Category 5e | Data | 1 Gbps |
| Category 6 | Data | 1/10 Gbps |
Optical Fiber Cabling
Optical Fiber cables use optical fibers that carry digital data signals in the form of modulated pulses of light. An optical fiber consists of an extremely thin cylinder of glass, called the core, surrounded by a concentric layer of glass, known as the cladding. There are two fibers per cable—one to transmit and one to receive. The core also can be an optical-quality clear plastic, and the cladding can be made up of gel that reflects signals back into the fiber to reduce signal loss.
There are two types of fiber optic cable: Single Mode Fibre (SMF) and Multi Mode Fibre (MMF).
1. Single Mode Fibre (SMF) uses a single ray of light to carry transmission over long distances.
2. Multi Mode Fibre (MMF) uses multiple rays of light simultaneously with each ray of light running at a different reflection angle to carry the transmission over short distances.
Read more: http://vusolutions.com/2012/01/05/cs601-vu-current-assignment-no-04-semester-fall-2011-solution-soon/#ixzz1ikOZapfi
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