Coaxial cable
                              Coaxial cable carries signals of higher frequency ranges than twisted-pair cable. Coaxial cable has a central core conductor of solid or stranded wire (copper) enclosed in an insulating sheath and encased in an outer conductor of metal foil, braid, or a combination of the two (usually copper).  The outer metallic wrapping serves both as a shield against noise and as the second conductor and completes the circuit.  This outer conductor is also enclosed in an insulating sheath, and the whole cable is protected by a plastic cover.

  • Frequency range of coaxial cable from 100KHz to 500MHz.

Types of Coax standards
            The Coaxial cables are rated by a factor named radio government (RG) ratings.  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.
The few common RG rating standards are given below,

Fiber Optic media
                        It is a technology that uses glass (or plastic) threads (fibers) to transmit data.  A fiber optic cable consists of a bundle of glass threads, each of which is capable of transmitting messages modulated onto light waves. 

Several Aspects of light:

  • Nature of light à Light, a form of electromagnetic energy, travels at 300,000 kilometers/second, or approximately 186,000 miles/second, in a vacuum.  
  • Refraction à If a light ray traveling through one substance suddenly enters another (more or less dense) substance, its speed changes abruptly, causing the ray to change direction.  This change is called refraction.
  • Critical angle à A light beam moving from a more dense into a less dense medium.  We gradually increase the angle of incidence then the angle of refraction also increase, at some point the reflected beam on the second medium lying along the horizontal.  This incident angle at this point is known as critical angle.

  • Reflection à When the angle of incidence becomes greater than the critical angle, a new phenomenon occurs called reflection


Propagation Modes:


Fiber optics has several advantages over traditional metal communications lines:

  • Fiber optic cables have a much greater bandwidth than metal cables.  This means that they can carry more data.
  • Fiber optic cables are less susceptible than metal cables to interference.
  • Fiber optic cables are much thinner and lighter than metal wires.
  • Data can be transmitted digitally (the natural form for computer data) rather than analogically.

Disadvantage of fiber optics:

  • Expensive to install
They are more fragile than wire and are difficult to splice