Guided Media is also known as Wired or Bounded transmission media. A signal travelling the media is directed and confined by the physical limits of the medium.
Advantage of guided media
- More secure
- Provides high speed
- Used for shorter distances
Disadvantage of guided media
- Need Physical link
- Time Consuming
Three Types of Guided Media
There are three types of guided media which are Twisted-Pair Cable, Coaxial Cable and Fiber-Optic Cable are explained below.
Twisted-Pair Cable consists of two insulated conductors wire wound (normally copper), twisted together. In which one wire is to carry the signal to destination and other is used as a ground reference. Twisting is done so that the noise will equally affect the wire from the external environment.
Advantage of Twisted Pair Cable
- The frequency range is 0 to 3.5 kHz
- Repeater spacing is 2 KM
Disadvantage of Twisted Pair Cable
- No capacity to carrying a signal over long distances without the use of repeaters.
- Not suitable for broadband applications because of low bandwidth capacity.
- Poor security and easy to tap.
Applications of Twisted Pair Cables
- It is used in telephone lines.
- Also used in the DSL line (ADSL)
- ISDN (Integrated Services Digital Network).
Types of twisted pair cable
Unshielded Twisted-Pair Cable
Unshielded Twisted-Pair Cable is the widely used twisted-pair cable used in telecommunications as Ethernet cables and telephone wires.
UTP cables consist of 2 pairs of twisted cable use RJ-11 connector and cables consist of 4 pairs use an RJ-45 connector
Advantages of Unshielded Twisted-Pair Cable
- Higher data rates
- Easy to set up and install
- Flexible and low-cost media
Disadvantages of Unshielded Twisted-Pair Cable
- Limited bandwidth
- Susceptible to noise and cross talk
Shielded Twisted-Pair Cable
This type of cable consists of a special braided metal foil to block external interference.
Advantages of Shielded Twisted-Pair Cable
- Better performance at a higher data rate
- Eliminates cross talk
- Comparatively faster
Disadvantages of Shielded Twisted-Pair Cable
- Difficult to manufacture and install
- Bulky and expensive
- It is used in telephone lines to provide data and voice channels.
Coaxial cable has a central core conductor of stranded or solid wire (usually copper) enclosed in an insulating protection cover, which is, in turn, encased in an outer conductor of metal foil or a combination of the two. The outer metallic work as a shield against noise and as a conductor, which complete the circuit. The whole cable is covered by a plastic cover.
Two types of Coaxial Cable
- BaseBand: (50 ohms) used for digital transmission.
- BroadBand: uses for analog transmission on standard TV cable.
Coaxial cable advantages
- Carries signals of higher data rate and bandwidth.
- Used in analog telephone networks and traditional Cable TV networks.
Coaxial cable disadvantages
- The network depends on a single cable.
- Expensive and difficult to install when compared with twisted pair.
Applications of Coaxial cable
- Used in analog telephone networks, could carry 10,000 voice signals.
Fiber-Optic Cable is made of glass and transmits of data is based on the concept of reflection of light through glass. A glass core is surrounded by less dense glass called cladding.
Two types of Propagation Modes
Multiple light beams from a light source move through the core in different paths.
It is implemented in two forms: step-index and graded-index.
(a) Step-index: density of the core remains constant from the centre to the edges.
(b) Graded-index: decreases this distortion of the signal through the cable
Single-mode uses step-index fiber and a focused source of light which limits beams to a small range of angles, all close to the horizontal.