Bounded transmission media use “cabling” system that guides the data signals along a specific path. The most common guided media are: twisted pair cable, coaxial cable and optical fibre cable.
Twisted Pair Cable
It is made from a pair of copper wires twisted to each other and finally surrounded by outer insulating jacket. One wire of the pair is used for receiving data signal and the other wire is used for transmitting data. The wires are twisted in order to reduce unwanted noise and interference from external sources. It is used for both analog and digital transmission. It is available in different categories such as: category 4. Category 5, category 6 and category 7 depend on the bandwidth of the cables. The category 1, category 2 and category 3 are not used these days. It is available in two forms: unshielded twisted pair (UTP) and shielded twisted pair (STP).
Unshielded Twisted Pair (UTP): UTP cable is commonly used in telephone system. It transmits both data and voice. It consists of two conductors (copper0, each with its own color plastic insulation. UTP cable has lower bandwidth maximum up to 10 Mbps and it may interfere by the external sources. But it is less expensive and easy to use than any other cables.
Shielded Twisted Pair (STP): STP cable is commonly used in LAN for digital data transmission. It has metal foil or braided mesh covering each pair of insulted conductors. It prevents the penetration of electromagnetic noise from external sources. It has more bandwidth 100Mbps up to 1000Mbps.
- It is inexpensive and suitable for digital data transmission.
- It is easier for clamping connector and flexile for wring purpose.
- It has higher data transfer rate up to Gbps (Gigabits Per Second).
- It is not possible to transmit data for long distance (maximum up to 200).
- It emits electromagnetic interference.
- It is not suitable for analog data such as video transmission.
Coaxial cable is commonly used in cable TV in our home. It consists of two conductors. The inner copper conductor is surrounded by an insulator over which a sleeve of copper mesh in women. This copper mesh is again surrounded by PCV jacket. It spans longer distance at higher speed than unshielded twisted pair cable. It is availed in two forms: thinner coaxial cable and thicknet coaxial coax.
Thinner coaxial cable: It is also known as 10Base2 which refers to the specifications for thinnet coaxial cable carrying 10 Mbps signals maximum up to 200 meters. This cable is popular in bus topology network.
Thicknet coaxial cable: It is also known as 100Base5 which refers to the specifications for thicknet coaxial cable carrying 100Lbps signal up to 500 meter. This cable is popular in Cable TV network.
- It as higher bandwidth than unshielded twisted pair cable.
- It is less effective by electromagnetic interference.
- It can support multiple channels in a medium.
- It is expensive than unshielded twisted pair cable.
- It is inflexible and not suitable for digital data transmissions.
- It is easily tapped.
Optical Fiber cable
Optical fiber cable is made up of glass or plastic that transmits signals in the form of light. It is made up of a light conducting glass or plastic core through which light propagates. The core is surrounded by a glass cladding with lower index of refraction than the core to keep the light source in the core. Next a thin plastic jacket is used to protect the cladding. Fibers are typically grouped in bundle, protected by an outer sheath.
- They are suitable for long data transmission with unlimited bandwidth more than Gbps than any other cables.
- They are much thinner and lighter than the others.
- Data is transmitted in the form of light, so it is difficult to tap from the middle of cable.
- They are not affected by outer interference such as electromagnetic interference.
- They are not so flexible than other cables, so it is difficult to bend.
- They are expensive than the others.
- It is very difficult to connect two fibre optic cables.
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