Transmission Media

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1- Describe each type of guided transmission media (structure, characteristics, pictures, examples) 1) Twisted Pair:
Most common medium, two separately insulated copper wires twisted together and it’s often “bundled” into cables. * Unshielded Twisted Pair (UTP)
- Ordinary telephone wire
- Cheapest
- Easiest to install.
- Suffers from external EM interference
* Shielded Twisted Pair (STP)
- Metal braid or sheathing that reduces interference
- More expensive
- Harder to handle (thick, heavy)

2) Coaxial cable:
* Central conductor - usually copper.
* Inner conductor wire surrounded by insulation (dielectric) * A metallic outer conductor (shield), serves as a ground. * An insulator covering the centre conductor.
* A plastic jacket.
* Most versatile medium
* Traditional cable television, exclusively transmitting in one direction, was composed completely of coax cable. * Long distance telephone transmission
* Can carry 10,000 voice calls simultaneously
* Being replaced by fiber optics, microwave & satellite * Attaches antennas to wireless devices. The coaxial cable carries radio frequency (RF) energy between the antennas and the radio equipment. * Local area networks, but now replaced by UTP.

3) Optical Fiber:
- Optical Signal is carried by photon pulses through thin (8 to 10 microns) glass strands (optical fibers), light waves are produced either by Light emitting diodes (LEDs) or injection laser diode (ILD). at transmitting and receiving end, signal is converted from and reconverted to electrical form by optical modems such as an avalanche photo diode. Greater capacity: Data rates of hundreds of Gbps

Smaller size & weight
Lower attenuation
Electromagnetic isolation
Greater repeater spacing: 10s of km at least
Immunity to corrosive materials
More immune to tapping
* Long-haul trunks: about 1500 km in length & 20,000-60,000 voice...
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