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Transmision media


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

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

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