The means through which data is transformed from one place to another is called transmission or communication media. There are two categories of transmission media used in computer communications.
Infrared transmission is usually limited to a small area, e.g. one room, with the transmitter pointed towards the receiver. The hardware is inexpensive and does not require an antenna.
A network that uses electromagnetic radio waves operates at radio frequency and its transmissions are called RF transmissions. Each host on the network attaches to an antenna, which can both send and receive RF.
Radio transmissions do not bend round the surface of the earth, but RF technology combined with satellites can provide long-distance connections. Figure 5 illustrates a satellite link across an ocean.
Twisted Pair Cable
The most popular network cabling is Twisted pair. It is light weight, easy to install, inexpensive and support many different types of network. It also supports the speed of 100 mps.
Fiber optic cable uses electrical signals to transmit data. It uses light. In fiber optic cable light only moves in one direction for two way communication to take place a second connection must be made between the two devices.
Electromagnetic radiation beyond the frequency range of radio and television can be used to transport information. Microwave transmission is usually point-to-point using directional antennae with a clear path between transmitter and receiver.
Coaxial cable is very common & widely used commutation media. For example TV wire is usually coaxial.