Transmision media


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Transmision Media Help to trasfer the data form One Place to Other Place....

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Transmision media

  1. 1. Transmission Media
  2. 2. Transmission Media <ul><li>two major classes </li></ul><ul><ul><li>Conducted or guided media </li></ul></ul><ul><ul><ul><li>use a conductor such as a wire or a fiber optic cable to move the signal from sender to receiver </li></ul></ul></ul><ul><ul><li>Wireless or unguided media </li></ul></ul><ul><ul><ul><li>use radio waves of different frequencies and do not need a wire or cable conductor to transmit signals </li></ul></ul></ul>
  3. 3. Classes of transmission media
  4. 4. Guided Media <ul><li>Twisted-Pair Cable </li></ul><ul><li>Coaxial Cable </li></ul><ul><li>Fiber-Optic Cable </li></ul>
  5. 5. Twisted Pair Wires <ul><li>Consists of two insulated copper wires arranged in a regular spiral pattern to minimize the electromagnetic interference between adjacent pairs. </li></ul><ul><li>Often used at customer facilities and also over distances to carry voice as well as data communications. </li></ul><ul><li>Low frequency transmission medium. </li></ul>
  6. 6. Copper Wires <ul><li>Primary medium to connect computers because </li></ul><ul><ul><li>Inexpensive & easy to install </li></ul></ul><ul><ul><li>Low resistance to electric current </li></ul></ul><ul><li>When wires placed close together in parallel, interference takes place </li></ul><ul><li>To minimize interference, networks use: </li></ul><ul><ul><li>Twisted pair </li></ul></ul><ul><li>Advantages </li></ul><ul><ul><li>Limits electromagnetic energy emission </li></ul></ul><ul><ul><li>Prevents signals from other wires from interfering </li></ul></ul>Plastic coated wires
  7. 7. Twisted Pair
  8. 8. Twisted-pair cable
  9. 9. Twisted Pair Wires <ul><li>Two varieties </li></ul><ul><li>UTP (unshielded twisted pair) </li></ul><ul><ul><li>Each wire is insulated with plastic wrap. </li></ul></ul><ul><ul><li>The plastic insulation is color-banded for identification. </li></ul></ul><ul><ul><li>UTP is ordinary telephone wire. </li></ul></ul><ul><ul><li>UTP can transfer data at 1 to 100Mbps over a distance of 100M. </li></ul></ul><ul><li>STP (shielded twisted pair) </li></ul><ul><ul><li>The pair is wrapped with metallic foil or braid to insulate the pair from electromagnetic interference. </li></ul></ul><ul><ul><li>The metal covering prevents the penetration of electromagnetic noise. </li></ul></ul><ul><ul><li>It can eliminate the phenomena called crosstalk. </li></ul></ul><ul><ul><li>Provide better performance at lower data rates. </li></ul></ul>
  10. 10. UTP & STP
  11. 11. Twisted Pair Wires <ul><li>Category 3 UTP </li></ul><ul><ul><li>data rates of up to 10mbps are achievable </li></ul></ul><ul><ul><li>Standard cable for most telephone systems </li></ul></ul><ul><li>Category 5 UTP </li></ul><ul><ul><li>data rates of up to 100mbps are achievable </li></ul></ul><ul><ul><li>more tightly twisted than Category 3 cables </li></ul></ul><ul><ul><li>more expensive, but better performance </li></ul></ul><ul><ul><li>Used in LAN. </li></ul></ul><ul><li>STP </li></ul><ul><ul><li>More expensive, harder to work with </li></ul></ul>
  12. 12. Twisted Pair <ul><li>(a) Category 3 UTP. </li></ul><ul><li>(b) Category 5 UTP. </li></ul>
  13. 13. Twisted Pair - Applications <ul><li>Most common medium </li></ul><ul><li>Telephone network </li></ul><ul><ul><li>Between house and local exchange (subscriber loop) </li></ul></ul><ul><li>Within buildings </li></ul><ul><ul><li>To private branch exchange (PBX) </li></ul></ul><ul><li>For local area networks (LAN) </li></ul><ul><ul><li>10Mbps or 100Mbps </li></ul></ul>
  14. 14. Twisted Pair Advantages <ul><li>Twisted-pair cable is used in telephone lines for voice and data communications. </li></ul><ul><li>Inexpensive and readily available </li></ul><ul><li>Flexible and light weight </li></ul><ul><li>Easy to work with and install </li></ul>
  15. 15. Twisted Pair Disadvantages <ul><li>Susceptibility to interference and noise </li></ul><ul><li>Attenuation problem </li></ul><ul><ul><li>For analog, repeaters needed every 5-6km </li></ul></ul><ul><ul><li>For digital, repeaters needed every 2-3km </li></ul></ul><ul><li>Relatively low bandwidth (3000Hz) </li></ul>
  16. 16. Coaxial Cable (or Coax) <ul><li>Carries the signal of high frequency ranges than twisted pair cable, </li></ul><ul><li>Bandwidth of up to 400 MHz. </li></ul><ul><li>Coaxial cable has the following layers (starting from the center): a metallic rod-shaped inner conductor, an insulator covering the rod, a metallic outer conductor (shield), an insulator covering the shield, and a plastic cover. </li></ul><ul><li>Both conductors share a common center axial, hence the term “co-axial”. </li></ul>
  17. 17. Coaxial cable
  18. 18. Classification: <ul><li>Coaxial cable is classified by size (RG) and by the cable resistance to electric currents. </li></ul><ul><li>Following are some coaxial cable commonly used in networking. </li></ul><ul><ul><li>50 ohm , RG-8 and RG-11 for Ethernet. </li></ul></ul><ul><ul><li>75 ohm , RG-59 used for cable TV. </li></ul></ul><ul><li>Transmission rate is 10 mbps. </li></ul>
  19. 19. Coax Advantages <ul><li>Easy to install </li></ul><ul><li>Coaxial cable is used in cable TV networks and traditional Ethernet LANs. </li></ul><ul><li>Higher bandwidth </li></ul><ul><ul><li>400 to 600Mhz </li></ul></ul><ul><li>Easy to handle and relatively inexpensive as compared to fiber optic cables. </li></ul><ul><li>Since it is shielded can span a longer distances at higher data rates. </li></ul><ul><li>Excellent noise immunity. </li></ul><ul><li>Much less susceptible to interference than twisted pair. </li></ul>
  20. 20. Coax Disadvantages <ul><li>High attenuation rate makes it expensive over long distance </li></ul><ul><li>Distance is limited. </li></ul><ul><li>Bulky </li></ul><ul><li>Higher cost compared to twisted pair </li></ul><ul><li>Harder to work with & cable easily get damaged </li></ul>
  21. 21. Fiber Optic Cable <ul><li>Fiber-optic cables are composed of a glass or plastic inner core surrounded by cladding, all encased in an outside jacket. </li></ul><ul><li>Fiber-optic cables carry data signals in the form of light. The signal is propagated along the inner core by reflection. </li></ul><ul><li>Relatively new transmission medium used by telephone companies in place of long-distance trunk lines. </li></ul><ul><li>Also used by private companies in implementing local data communications networks. </li></ul><ul><li>Require a light source with injection laser diode (ILD) or light-emitting diodes (LED). </li></ul>
  22. 22. Fiber Optic Layers <ul><li>consists of three concentric sections </li></ul>plastic jacket glass or plastic cladding fiber core
  23. 23. Refraction
  24. 24. Critical Angle
  25. 25. Reflection
  26. 26. Refraction & Reflection
  27. 27. Fiber Optic Types <ul><li>Signal propagation in optical fibers can be multimode (multiple beams from a light source moves through different path) or single-mode (essentially one beam from a light source). </li></ul><ul><li>Multimode step-index fiber </li></ul><ul><ul><li>In multimode step-index propagation, the core density is constant and the light beam changes direction suddenly at the interface between the core and the cladding. </li></ul></ul><ul><li>Multimode graded-index fiber </li></ul><ul><ul><li>In multimode graded-index propagation, the core density decreases with distance from the center. This causes a curving of the light beams. </li></ul></ul>
  28. 28. <ul><li>Single mode fiber </li></ul><ul><ul><li>This uses step-index fiber and a highly focused source of light </li></ul></ul><ul><ul><li>Has very low density,which make c=90,so beam becomes almost horizontal. </li></ul></ul>
  29. 29. Fiber Optic Signals fiber optic multimode step-index fiber optic multimode graded-index fiber optic single mode
  30. 30. Fiber Optic Advantages <ul><li>Higher transmission rate of 100Mbps. </li></ul><ul><li>It supports voice,video and data. </li></ul><ul><li>Greater capacity (bandwidth of up to 2 Gbps). </li></ul><ul><li>Smaller size and lighter weight </li></ul><ul><li>Lower attenuation </li></ul><ul><li>Immunity to environmental interference </li></ul><ul><li>Highly secure , it is almost impossible to tap into a fiber cable. </li></ul><ul><li>Safe and easy installation. </li></ul><ul><li>More compact & lighter than copper wire </li></ul>
  31. 31. Fiber Optic Disadvantages <ul><li>expensive over short distance </li></ul><ul><li>Unidirectional </li></ul><ul><li>requires highly skilled installers </li></ul><ul><li>adding additional nodes is difficult </li></ul><ul><li>Maintenance and repairing cost is high. </li></ul>