Transmission media: When a PC communicates or wants to communicate with another PC, it has to take the help of some transmission media. The most commonly used media in the network are twisted pair cable, coaxial cable, fiber optic cable. Nowadays, the use of optical fiber is increasing greatly. Radio wave, microwave and infrared technologies are prominent among wireless media. Among these mediums, optical fiber has the highest data transfer speed. The type of medium used in a network depends on the type and location of that network. The connection system for exchanging information between the sender and the remote receiving end is called a channel. The means or methods used to implement the channel are called media. such as--
(i) Cable or wire.
(ii) Common telephone lines.
(ii) Radio waves.
(iv) Microwave.
(v) Geo-satellite systems etc.
Cable or Wire: Cable is an important medium in data communication. Cables are generally used for data transfer over short range networking such as LAN (Local Area Network). But on a larger scale, such as WAN (Wide Area Network) high speed data communication, cables are also used. There are different types of cables. There are three types of cables in data communication --
(i) Twisted Pair Cable
(ii) Coaxial Cable
(iii) Fiber Optic Cable
Twisted pair cable: Twisted pair is made by twisting two conductors evenly. A dielectric material is used to separate the two twisted conductors. A total of 4 pairs of wires are usually used in this type of cable. Each pair of wires has a common color (white) wire. Other wires are different colors. 1, 2, 3, 4, 5, 6, 7, 8 need to be connected based on the number of wires. Each pair of wires has a thickness of 0.4 mm to 0.9 mm.
Advantages of twisted pair:
(i) It is very cheap in price.
(ii) It is also easy to install in the system.
Disadvantages of twisted pair:
(i) Such cables are generally used for transmitting data over a distance of 100 m.
(ii) The rate of data transfer decreases as the data transfer distance increases.
(iii) Tripmit loss of such cables is very high.
Uses of twisted pairs:
Twisted pair cables are widely used as communication cables. such as--
(i) This wire is used in telephone lines.
(ii) Such cables are used in digital signaling and LAN. Data transmission rate for LAN is 10Mbps,
Twisted pair cables are of two types namely--
(i) Unshielded Twisted Pair or UTP
(ii) Shielded Twisted Pair or STP
Co-axial Cable: Coaxial cable is commonly known as coaxial. Coaxial cable is made up of two conductors and dielectric materials. A solid copper core runs through the center of the coax cable, with an insulating material between them to cover the center conductor and separate the outer conductors. The outer conductor is covered by a plastic jacket. The data transfer speed of this type of cable is high. But the data transfer rate depends on the length of the cable. Digital data can be transmitted over distances of up to one kilometer using coaxial cables. In this case the data transmission rate can be 1-2bps. The transmission loss of this type of cable is relatively less.
Coaxial cables are of two types, namely- (i) Thinnet, (ii) Thicknet.
Fiber optic cable: Fiber optic cable is a type of fiber made of di-electronic insulating materials, which is capable of registering and transporting light. Data is exchanged through such cables at the speed of light and laser beams are used for the exchange.
Structure of fiber optic cable: Fiber optic cable consists of three main parts, namely-
(a) Core: The innermost part is the core, which is made of glass or plastic up to 100 micrometers. The core does the main job of transmitting light signals. The refractive index of the core is high.
(b) Cladding: The outer part of the core is the cladding. Cladding is a special coating made of glass or plastic that reflects light emitted by the core and sends it back to the core. The refractive index of the cladding is less than the refractive index of the core.
(c) Jacket: The outermost part made of plastic and various metallic materials is the jacket. The jacket protects the fiber from water vapor, humidity, abrasion, twisting and other natural disasters.
Fiber optic cables are currently available in the market, with transmission rates ranging from 100 mbps to 2 giga bps. Nowadays, intercontinental fiber optic cables are laid under the ocean floor to transport large amounts of data.
Constituent elements of fiber:
Silica and multi-component glass are used as insulating materials for fiber. The salient features of all these insulating materials are given--
(i) Energy wastage is reduced,
(ii) chemical inertness,
(iii) easy feminization,
(iv) ultra-transparency,
(v) Capable of fast data exchange.
The most common multi-component glasses in optical fibers are Sova, Boro Silicate, Soda Alumina Silicate, Sodalime Silicate etc. Sometimes plastic is used as a fiber cladding.
Features of fiber optic cable:
(i) It transmits light signals instead of electrical signals.
(ii) Can transmit data at very high speed.
(iii) Energy loss is relatively less.
(iv) Energy wastage is reduced.
(v) Free from electromagnetic influence.
(vi) It is mostly used as the backbone of the network.
Advantages of using fiber optic cable:
(i) Data transfer speed is very high.
(ii) It weighs less.
(iii) Data is transferred at the speed of light.
(iv) Less volume of cable.
(v) Energy loss is less.
(vi) Transfer data accurately.
(vii) Confidentiality can be maintained to preserve information.
(viii) The environment may not interfere with data transfer due to heat, pressure etc.
Disadvantages of using fiber optic cable:
(i) Fiber optic cables are very expensive. But gradually with the development of technology, this price is coming down.
(ii) Installation of fiber optic cable is relatively troublesome than other cables.
(iii) Fiber optic cable cannot be bent like English letter B.
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