DATA COMMUNICATION Lecture-26

Recap of Lecture 25 Guided Media Twisted Pair Coaxial Cable Optical Fiber

Overview of Lecture 26 Guided Media Optical Fiber Cable Unguided Media Radio Frequency Allocation Propagation of Radio Waves

Single Mode Fiber Uses step-index fiber and a highly focused source of light The core has a much smaller diameter and a low density ( critical angle is close to 90 degrees)

Single Mode Fiber

Fiber Sizes Defined by the ratio of the core diameter to the cladding diameter, expressed in microns

Fiber Sizes Common Fiber Types Fiber type Core Cladding 62.5/125 62.5 125 50/125 50 125 100/140 100 140 8.3/125 8.3 125

Cable Composition Fiber = core + cladding (both are glass or plastic) Core: Ultra-pure and completely regular in size and shape Outer jacket can be made of plastic, metal or Teflon

Cable Composition

Cable Composition Fiber = core + cladding (both are glass or plastic) Core: Ultra-pure and completely regular in size and shape Outer jacket can be made of plastic, metal or Teflon

Light Sources LED(Light Emitting Diode) ILD(Injection Laser Diode) Cheap Unfocused light Uncontrollable For short-distance use ILD(Injection Laser Diode) Focused light Long distance

Fiber Connectors Must be precise Misalignment results in the signal reflection An overly tight connection can compress the cores and alter the reflected angle

Advantages of Optical Fiber Noise resistance Less signal attenuation Higher bandwidth

Disadvantages of Optical Fiber Cost Installation/Maintenance Fragility

Unguided Media Transportation of Electromagnetic waves without a physical conductor Signals are broadcast through Air Available to anyone who has a receiver capable of receiving them

Radio Frequency Allocation

Types of Propagation

Summary Guided Media Optical Fiber Cable Unguided Media Radio Frequency Allocation Propagation of Radio Waves

Suggested Reading Section 7.1,7.2 “Data Communications and Networking” 2nd Edition by Behrouz A. Forouzan