The type of communication media in which communication devices are directly linked with each other via cables or physical media is called Guided media. The data signals are bounded to cabling media. Therefore, guided media is also called Bounded media. The examples of guided or bounded media are:
- Twisted pair wire
- Coaxial cable
- Fiber optic cable
1- Twisted Pair Cable
Twisted Pair Cable is one of the most commonly used communication media. It consists of a copper wires. These wires are covered by insulating material (such as plastic). The wires are twisted around each other. Twisting of wires protect them from interference by external electromagnetic waves.
A twisted pair cable is used for short distance digital data transmission. Its data transmission speed is about 9600 bits per second in a distance of 100 meters. It is commonly used in local area network (LAN). It is also used in telephone lines to carry voice and data signals.
2- Coaxial Cable
Coaxial cable is also called Coax. It consists of a copper wire, which is called the inner conductor. Usually, the inner conductor is surrounded by three layers:
- An insulting material, which covers the inner conductor.
- The insulted inner conductor is surrounded by copper shield called outer conductor.
- An insulting material, which covers the outer conductor.
The whole cable is protected by an external plastic cover. These layers protect the cable from interference by external electromagnetic waves.
Coaxial cables are mainly used for telephone lines and local area networks. These cables can transfer data with very high frequency. The bandwidth of coaxial cable is 80 times greater than that of twisted pair media. It is more expensive than twisted pair wire.
3- Fiber Optic Cable
The fiber optic cable uses light to transmit data. It consists of a very narrow strand or fiber of glass called the core. It is as thin as a human hair. The core is surrounded by a concentric layer of glass called cladding. The cladding is further protected by plastic coating called the Jacket. An important characteristic (or property) of fiber optic is refraction. Refraction is the characteristic of a material to either pass or reflect light.
The fiber optic cable is not affected by electromagnetic waves. It is more reliable and has lower data transmission errors. The data transmission speed is very high. It is up to billions bits per second. However, it is costly. Today, most of the telephone companies, ISP companies and cable TV operators are using fiber optic cables in their networks.