Guided Media

Guided media are that kind of media in which transmission through cables. Three guided media commonly used for data transmission are Twisted pair, Coaxial Cable, and  Optical fiber. The least expensive and most widely used guided transmission medium is the Twisted pair.

 

Twisted Pair Wire

Twisted pair wire consist of two bunches of thin copper wire, each bunch enclosed separately in plastic insulation, then twisted around each other to reduce interference by adjacent wires. It is also called unshielded twisted-Pair (UTP) cable because other than the plastic coating around the two individual bunches of copper wires, nothing shields it from outside interference.

UTP cables are used in local telephone communication and short distance ( up to about 1 km) digital data transmission. They are normally used to connect terminals to the main computer if they are placed at a short distance from the main computer. The data transmission speed of up to 9600 bit per second ( 9600 band0 can be achieved if the distance isn't more than 100 meters. Normally speed of digital signal transmission is 1200 bits per second.

Twisted Pair

   

Pros

1. In-Expensive medium of data transmission
2. Easy to configure

Cons

1. Easily pick up noise signals
2. High error rates when cable extends beyond 100 meters.

Coaxial Cable

Coaxial cables are groups of specially wrapped and insulated wire lines that can transmit data at high rates. they consist of a central copper wire surrounded by a PVC(Plastic rubber) insulation over which a sleeve of copper mesh is placed the metal sleeve is again shielded by an outer shield of thick PVC material. The signal is transmitted by the inner copper wire and is electrically shielded by the outer metal sleeve.

Coaxial Cable

Coaxial cable offers much higher bandwidths than UTP cables and is capable of transmitting digital signals at rates of 10 megabits per second. They are extensively used in long-distance telephone lines and as cables for cable TV.

Optical Fibers

Optical Fiber

Optical fiber is hair-thin threads of glass or plastic that can serve as a data transmission medium as copper wires or coaxial cables. The basic difference it heats optical fiber transmits light signals instead of electrical signals because light travels much faster than electricity, Optical fibers can transmit data at a much higher speed than copper wires or coaxial cables, and also with no significant loss of intensity over a long distance.

In Optical Fibers, we need one converter that converts electrical signals into light waves. The converter uses either a light-emitting diode(LED) or a laser diode to convert electric signals into light signals.