Transmission Media - (1)

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Transmission Media - 1


Objectives :

  1. Cable characteristics
  2. Various types of Cables 
  3. Fiber optic cable 
  4. Connectors of fiber optic cable 
  5. Cabling Standard - EIA/TIA 568A and 568B 
  6. Straight cabling & Cross Cabling 


Introduction :-

      Networking involves connection of computers, workstations and peripheral devices. Networking hardware involves all the peripheral devices,interface cards and other equipment such as cables and wires that are used to establish a network connection. Wire is a single, cylindrical strand of metal conductor with low resistance to the current flow. Cable can be defined as a bunch of wires bound together which may be or insulted. You can connect these devices either using physical transmission medium or using wireless transmission medium. Physical transmission media involves the use of wires and cables.


(1) Characteristics of Cables :

      Before selecting a cable for a networking, you may have to consider various cable characteristics. Every cable has certain advantages and disadvantages. You may  have to consider the following criteria before selecting and installing a network cable:

  • Segment length - Every cable has a limitation to carry signals only to a particular distance after which the quality of the signal degrades and becomes corrupt. The capacity of the cable to carry signals to a certain distance till they can be regenerated using amplifiers or repeaters is known as the maximum segment length of that cable.
  • Attenuation - As the signals travel through cables, they lose their strength. This loss of signal strength in a cable is called as attenuation. With more attenuation , the signal strength arriving destination decreases  the operating frequency and cable length increases, attenuation also increases. Attenuation is measured in DB( decibels ) and expressed as a negative value as it indicates a loss, for example -12 DB.
  • Bandwidth -It is the amount of digital data that a cable can carry. Each type of cable can carry only a certain amount of information or data over a given period of time. This capacity is measured in terms of bandwidth. It is measured in the terms of bits or bytes the cable can carry at the certain time. It is an important factor while selecting a network cable.
  • Cost - Cables come in different quality. Depending on the length, size of the network, you may need to choose the right type of cable. Copper cable are the cheapest form of cable, whereas fiber optic cable are the most expensive. Installation costs of copper cables are cheaper as compared to that of fiber optic cables.
  • Interference susceptibility - Each type of cable is susceptible to some interference such as internal or external noise. It depends on the environment where the cable is to be laid. External noise may consist of Electromagnetic interference (EMI) or Radio frequency interference (RFI). EMI refers to unwanted radiations or noise from external devices such as electric motors and relays. RFI  refers to the radiation in the radio frequency range interfering the transmissions over copper cables. In case of shielded cable, if the shield is not grounded properly, then it acts as an antenna and picks up such interfering signals. Cables that consist of shielding are less susceptible to interference than the unshielded cables. Coaxial cables shielded twisted pair cables are less susceptible to interference. Fiber optic cables are the least susceptible to interference.
    • Crosstalk - It is the interference caused when magnetic field generated by the current flowing through one cable affects electrical currents of other cable. Cable crosstalk can result in signal distortion which leads towards network problems. Crosstalk can be reduced by twisting and shielding the wire pairs. In twisted pair cable the magnetic fields cancel each other to decrease the crosstalk.


    (2) Types of cables :- 

           There are different mediums available for transferring data over the network. Data transferred through copper wires by converting appropriate electrical signals. Copper wires are cheapest mode of cable available. 
      
           There are various types of copper transmission medium available depending on the size of networks and the individual needs. The types of cable used for the networking are :
    1. Coaxial cables ( also known as Co-ax)
    2. Twisted pair Cables ( TP )
    • Unshielded Twisted pair ( UTP )
    • Sheilded Twisted pair ( STP )
        3. Fiber Optic Cables (FOC)


    Credit : Rinika Bera 

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    Have a GOOD DAY !

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