Transmission Media

Transmission Media

There are two categories of Transmission Media:

  • Guided Media
  • Unguided Media

Guided Media: Guided media follow the fixed path for transmission. 

Example: Twisted-pair Cable, Coaxial Cabling, Fiber-optic cabling

Unguided Media : Media in which the signal ate not guided through solid medium are known as Unguided Media.

Example: Radio waves, Micro Waves, Infrared Waves

Twisted-pair Cable:

    • A twisted pair of wires consists of two insulated copper wires, typically about 1 mm thickness.
    • The wires are twisted together in a helical shape.
    • The purpose of twisting the wires is to reduce electrical interference.
    • Twisted pair wire are commonly used in local telephone communication and for digital data transmission over short distance up to 1 Km.
    • Twisted pair cabling, are of two types:
      • Unshielded twisted pair
      • Shielded twisted pair
    Coaxial Cable

      • Coaxial cables carry the signal of higher frequency range compared to twisted pair cable.
      • Coaxial cables are also cold coax (short form)
      • There are two type coaxial cables are widely used : 50 ohm and 75 ohm cable.
      • 50 ohm cable is used for digital transmission and 75 ohm cable used for analog transmission.
      Fiber Optic Cable

        • Fiber optic cable is made of glass strands that transmit signals as light waves or pulses.
        • Each fiber is surrounded by a plastic sheath.
        • Fiber optic cable is generally used for backbone for high speed interconnection between networking devices.
        • Fiber optic cable can easily handle data at speeds above 1Gbps, it has been demonstrated to handles above data rate exceeding 200Gbps.
        • It can handle much higher bandwidth than copper.
        • Fiber is lighter than copper.
        Unguided media

          • Media in which the signals are not guided through a solid medium are known as unguided media.
          • Air is the media through which electromagnetic energy can flow easily.
          • Therefore, there are several methods which are in use to send electromagnetic energy through air. 
          • These methods are:
            • Radio waves
            • Micro waves
            • Infrared Waves
          Radio waves

            • Electromagnetic waves ranging in frequencies between 10 Kilohertz and 1 gigahertz. 
            • Radio waves can be broadcasted Omni directional or  unidirectional.
            • Various kind of antennae can be used to broadcast radio signals.
            • Radio waves are easy to generate.
            • They can travel long distance.
            Microwave

              • Above 100 MHz, the waves travel in straight lines and can therefore be narrowly focused.
              • Concentrating all the energy into a small beam using a parabolic antenna (like the satellite TV dish) gives much higher signal to noise radio.
              • They are used in Cellular phones, satellite networks and wireless LANs.
              Infrared

                • Unguided infrared and millimeter waves are widely used for short-range communication.
                • The remote controls used on television, VCRs used infrared communication.
                • They are relatively directional, cheap and easy to build but do not pass through solid objects.
                • Infrared communication is used for indoor wireless LANs.
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