Networking Media: Fiber Optics and Radio Waves

Fiber Optics

• Fiber Optic Cable Structure

  • Composed of two strands, typically one blue and one red.
  • Each strand contains a thin glass fiber.
  • Surrounding the glass fiber is a coating of cladding, a different type of glass.
  • The cladding has a slightly different refractive index than the fiber strand.

• Mechanism of Transmission

  • Light, usually from a laser, is sent through the fiber.
  • Due to the refractive index difference, total internal reflection occurs.
  • Light refracts off the edge, allowing it to travel through the fiber, even around corners.

• Demonstration of Light Transmission

  • Example: Red laser light sent through blue fiber and visible at the other end.
  • Sometimes infrared light is used in networking.

• Encoding Information

  • Light on/off can represent different symbols.
  • Pulsing light on/off enables sending information using on-off keying.

Radio Waves

• Wireless Transmission

  • Example: Wireless router with an antenna.
  • Antenna is essentially a wire or coil of wire.

• Mechanism of Transmission

  • Voltage in the antenna varies at high frequency (e.g., 2.4 GHz sine wave).
  • This variation causes the antenna to radiate radio waves.

• Receiving and Decoding Signals

  • Another device receives radio waves, amplifies them, and converts back into the signal.

• Phase Shifting for Encoding

  • Phase of the sine wave can be shifted (e.g., 180-degree phase shift).
  • In-phase signal might represent a '0', out-of-phase signal a '1'.
  • By rapidly shifting phases, ones and zeros can be transmitted over radio waves.

Summary

• Fiber optics and radio waves are common media for transmitting data in networks.
• Both use different physical properties and techniques to encode symbols for data transmission.