1. DATA COMMUNICATION
Lecture-26

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

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

4. 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)

5. Single Mode Fiber

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

7. Fiber Sizes Common Fiber Types Fiber type Core Cladding
62.5/
50/
100/
8.3/

8. 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

9. Cable Composition

10. 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

11. 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

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

13. Advantages of Optical Fiber
Noise resistance
Less signal attenuation
Higher bandwidth

14. Disadvantages of Optical Fiber
Cost
Installation/Maintenance
Fragility

15. 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

16. Radio Frequency Allocation

17. Types of Propagation

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

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