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Transmission Media Semester: 131 Course: CSET 221 Computer Networking Instructor: Farhan Khan Computer Science & Engineering Technology Unit Hafr Al-Batin.

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Presentation on theme: "Transmission Media Semester: 131 Course: CSET 221 Computer Networking Instructor: Farhan Khan Computer Science & Engineering Technology Unit Hafr Al-Batin."— Presentation transcript:

1 Transmission Media Semester: 131 Course: CSET 221 Computer Networking Instructor: Farhan Khan Computer Science & Engineering Technology Unit Hafr Al-Batin Community College

2 Outline Guided Media Guided Media Twisted-Pair Cable Twisted-Pair Cable UTP UTP STP STP Coaxial Cable Coaxial Cable Fiber-Optic Cable Fiber-Optic Cable Multimode Multimode Single Mode Single Mode Unguided Media Unguided Media Radio Waves Radio Waves Microwaves Microwaves Infrared Infrared 2

3 3 Physical Layer

4 Transmission Media and Physical Layer Computer and other telecommunication devices use signals to represent data. Computer and other telecommunication devices use signals to represent data. Signals are transmitted from one device to another in the form of electromagnetic energy, which is propagated through transmission media. Signals are transmitted from one device to another in the form of electromagnetic energy, which is propagated through transmission media. 4

5 5 Classes of Transmission Media

6 6 Guided Media Guided media are those that provide a conduit from one device to another. Guided media are those that provide a conduit from one device to another. Signal travelling along any of these media is directed and contained by the physical limits of the medium. Signal travelling along any of these media is directed and contained by the physical limits of the medium. Include Include twisted-pair cables twisted-pair cables coaxial cables coaxial cables fiber-optic cables fiber-optic cables

7 7 Twisted-Pair Cable

8 A twisted pair consists of two conductors (normally copper), each with its own plastic insulation, twisted together. A twisted pair consists of two conductors (normally copper), each with its own plastic insulation, twisted together. Twisting cancels out electrical noise from adjacent pairs (crosstalk) and from other noise sources. Twisting cancels out electrical noise from adjacent pairs (crosstalk) and from other noise sources. 8

9 9 UTP – Unshielded Twisted PairSTP –Shielded Twisted Pair UTP and STP Cables

10 STP cable has a metal foil or braided-mesh covering that encases each pair of insulated conductors. STP cable has a metal foil or braided-mesh covering that encases each pair of insulated conductors. Although metal casing improves the quality of cable by preventing the penetration of noise or crosstalk, it is bulkier and more expensive. Although metal casing improves the quality of cable by preventing the penetration of noise or crosstalk, it is bulkier and more expensive. 10

11 11 Categories of UTP/STP Cables

12 12 Categories of UTP/STP Cables CategoryBandwidthDigital/AnalogUse 1 very low AnalogTelephone 2 < 2 MHz < 2 MHzAnalog/digital 4Mbps token ring 3 16 MHz 16 MHzDigital Mbps Ethernet 4 20 MHz 20 MHzDigital 16 Mbps token ring MHz 100 MHzDigital 100 – 1000 Mbps Ethernet 5E 100 MHz Digital 100 – 1000 Mbps Ethernet MHz 250 MHzDigital 1 – 10 Gbps Ethernet 6A 500 MHz Digital 1 – 10 Gbps Ethernet MHz 600 MHzDigital 10 Gbps Ethernet 7A 1000 MHz Digital Gbps Ethernet

13 UTP Connectors RJ45 (Registered Jack) is the most common UTP connector. RJ45 (Registered Jack) is the most common UTP connector. RJ45 is a keyed connector, meaning the connector can be inserted in only one way. RJ45 is a keyed connector, meaning the connector can be inserted in only one way. 13 RJ – Registered Jack

14 14 Coaxial Cable

15 Coax has a central core conductor of solid or stranded wire (usually copper) enclosed in an insulating sheath, which is, in turn, encased in an outer conductor of metal foil, braid, or a combination of the two. Coax has a central core conductor of solid or stranded wire (usually copper) enclosed in an insulating sheath, which is, in turn, encased in an outer conductor of metal foil, braid, or a combination of the two. The outer metallic wrapping serves both as a shield against noise and as a second conductor, which completes the circuit. The outer metallic wrapping serves both as a shield against noise and as a second conductor, which completes the circuit. This outer conductor is also enclosed in an insulating sheath, and the whole cable is protected by a plastic cover. This outer conductor is also enclosed in an insulating sheath, and the whole cable is protected by a plastic cover. 15

16 Categories of Coaxial Cables Each Radio Government (RG) number denotes a unique set of physical specifications, including the wire gauge of the inner conductor, the thickness and type of the inner insulator, the construction of the shield, and the size and type of the outer casing. Each Radio Government (RG) number denotes a unique set of physical specifications, including the wire gauge of the inner conductor, the thickness and type of the inner insulator, the construction of the shield, and the size and type of the outer casing. 16 RG – Radio Government

17 17 BNC Connectors Bayonet Network Connector Bayonet Network Connector aka. Bayonet Neil-Concelman aka. Bayonet Neil-Concelman Used with coaxial cables Used with coaxial cables Three popular types are BNC connector, BNC T connector, BNC Terminator. Three popular types are BNC connector, BNC T connector, BNC Terminator.

18 18 Optical Fiber Fiber-Optic cable is made of glass or plastic and transmits signals in the form of light. Fiber-Optic cable is made of glass or plastic and transmits signals in the form of light. Based on physics of light Based on physics of light

19 Optical Fiber A glass or plastic core is surrounded by a cladding of less dense glass or plastic. A glass or plastic core is surrounded by a cladding of less dense glass or plastic. The difference in density of the two materials must be such that a beam of light moving through the core is reflected off the cladding instead of being refracted into it. The difference in density of the two materials must be such that a beam of light moving through the core is reflected off the cladding instead of being refracted into it. 19

20 Propagation Modes 20

21 Propagation Modes Multimode is so named because multiple beams from a light source move through the core in different paths. Multimode is so named because multiple beams from a light source move through the core in different paths. Multimode step-index fiber Multimode step-index fiber Density of the core remains constant from the center to the edges Density of the core remains constant from the center to the edges Beam of light moves through this constant density in a straight line until it reaches the interface of the core and the cladding. Beam of light moves through this constant density in a straight line until it reaches the interface of the core and the cladding. At the interface, there is an abrupt change to a lower density that alters the angle of the beams motion. The term step index refers to the suddenness of this change. At the interface, there is an abrupt change to a lower density that alters the angle of the beams motion. The term step index refers to the suddenness of this change. 21

22 Propagation Modes Multimode graded-index Fiber Multimode graded-index Fiber The word index here refers to the index of refraction that is related to density. The word index here refers to the index of refraction that is related to density. A graded-index fiber, is one with varying densities. Density is highest at the center of the core and decreases gradually to its lowest at the edge. A graded-index fiber, is one with varying densities. Density is highest at the center of the core and decreases gradually to its lowest at the edge. Single mode Fiber Single mode Fiber Single mode uses step-index fiber and a highly focused source of light that limits beams to a small range of angles, all close to the horizontal. Single mode uses step-index fiber and a highly focused source of light that limits beams to a small range of angles, all close to the horizontal. 22

23 23 Propagation Modes

24 24 Fiber Sizes

25 25 Fiber Construction

26 Outer jacket is made of either PVC or Teflon. Outer jacket is made of either PVC or Teflon. Inside the jacket are Kevlar strands to strengthen the cable. Kevlar is a strong material used in the fabrication of bulletproof vests. Inside the jacket are Kevlar strands to strengthen the cable. Kevlar is a strong material used in the fabrication of bulletproof vests. Below the Kevlar is another plastic coating to cushion the fiber. The fiber is at the center of the cable, and it consists of cladding and core. Below the Kevlar is another plastic coating to cushion the fiber. The fiber is at the center of the cable, and it consists of cladding and core. 26

27 27 Fiber-Optic Cable Connectors

28 Subscriber channel (SC) connector is used in cable TV. It uses a push/pull locking system. Subscriber channel (SC) connector is used in cable TV. It uses a push/pull locking system. Straight-tip (ST) connector is used for connecting cable to networking devices. It uses a bayonet locking system and is more reliable than SC. Straight-tip (ST) connector is used for connecting cable to networking devices. It uses a bayonet locking system and is more reliable than SC. MT-RJ is a new connector with the same size as RJ-45 MT-RJ is a new connector with the same size as RJ-45 28

29 Advantages of Fiber-Optic Cable Fiber-Optic cable has several advantages over metallic cable Fiber-Optic cable has several advantages over metallic cable Higher bandwidth, less signal attenuation, immunity to electromagnetic interference, resistance to corrosive materials, light weight, more immune to tapping. Higher bandwidth, less signal attenuation, immunity to electromagnetic interference, resistance to corrosive materials, light weight, more immune to tapping. Disadvantages: Installation/maintenance [need expertise], Unidirectional [propagation of light is unidirectional], Cost. Disadvantages: Installation/maintenance [need expertise], Unidirectional [propagation of light is unidirectional], Cost. 29

30 30 Unguided Media: Wireless Transport electromagnetic waves without using a physical conductor Transport electromagnetic waves without using a physical conductor Radio Waves Radio Waves Microwaves Microwaves Infrared Infrared Often referred to as wireless communication Often referred to as wireless communication

31 Electromagnetic Spectrum Figure shows the part of the electromagnetic spectrum, ranging from 3 kHz to 900 THz, used for wireless communication. Figure shows the part of the electromagnetic spectrum, ranging from 3 kHz to 900 THz, used for wireless communication. 31

32 32 Propagation Methods

33 Ground Propagation In ground propagation, radio waves travel through the lowest portion of the atmosphere, along the earth. In ground propagation, radio waves travel through the lowest portion of the atmosphere, along the earth. These low-frequency signals emanate in all directions from the transmitting antenna and follow the curvature of the planet. These low-frequency signals emanate in all directions from the transmitting antenna and follow the curvature of the planet. Distance depends on the amount of power in the signal: The greater the power, the greater the distance. Distance depends on the amount of power in the signal: The greater the power, the greater the distance. 33

34 Sky Propagation In sky propagation, higher-frequency radio waves radiate upward into the ionosphere (the layer of atmosphere where particles exist as ions) where they are reflected back to earth. In sky propagation, higher-frequency radio waves radiate upward into the ionosphere (the layer of atmosphere where particles exist as ions) where they are reflected back to earth. This type of transmission allows for greater distances with lower output power. This type of transmission allows for greater distances with lower output power. 34

35 Line-of-Sight Propagation In line-of-sight propagation, very high- frequency signals are transmitted in straight lines directly from antenna to antenna. In line-of-sight propagation, very high- frequency signals are transmitted in straight lines directly from antenna to antenna. Antennas must be directional, facing each other, and either tall enough or close enough together not to be affected by the curvature of the earth. Antennas must be directional, facing each other, and either tall enough or close enough together not to be affected by the curvature of the earth. 35

36 Bands The section of the electromagnetic spectrum defined as radio waves and microwaves is divided into eight ranges, called bands, each regulated by government authorities. The section of the electromagnetic spectrum defined as radio waves and microwaves is divided into eight ranges, called bands, each regulated by government authorities. These bands are rated from very low frequency (VLF) to extremely high frequency (EHF). These bands are rated from very low frequency (VLF) to extremely high frequency (EHF). 36

37 37 Bands

38 38 Wireless Transmission Waves

39 Radio Waves Radio waves are electromagnetic waves ranging in frequencies between 3 KHz and 1 GHz and those between 1 GHz and 300 GHz are called Microwaves. Radio waves are electromagnetic waves ranging in frequencies between 3 KHz and 1 GHz and those between 1 GHz and 300 GHz are called Microwaves. Radio waves Radio waves Are Omnidirectional; Propagate to long distances Are Omnidirectional; Propagate to long distances Can penetrate walls so we cannot isolate a communication to just inside or outside a building. Can penetrate walls so we cannot isolate a communication to just inside or outside a building. 39

40 Radio Waves 40 Radio waves are used for multicast communications, such as radio and television, and paging systems. They can penetrate through walls. Highly regulated. Use omnidirectional antennas

41 Omnidirectional Antenna 7.41

42 Microwaves 42 Microwaves are used for unicast communication such as cellular telephones, satellite networks, and wireless LANs. Higher frequency ranges cannot penetrate walls. Use unidirectional antennas - point to point line of sight communications.

43 Unidirectional Antennas

44 Infrared Infrared are electromagnetic waves ranging in frequencies between 300 GHz and 400 THz Infrared are electromagnetic waves ranging in frequencies between 300 GHz and 400 THz 44 Infrared signals can be used for short- range communication in a closed area using line-of-sight propagation.

45 Summary Guided Media Guided Media Twisted-Pair Cable Twisted-Pair Cable Coaxial Cable Coaxial Cable Fiber-Optic Cable Fiber-Optic Cable Unguided Media Unguided Media Radio Waves Radio Waves Microwaves Microwaves Infrared Infrared 45


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