Optical Communication

1. Engr. Abbas Abbasi
Optical Fiber
Theoretical Background

2. Optical Spectrum
First Generation: 0.8µ m to 0.9 µm
1.1 µ m to 1.6 µ m
 more wavelength , less losses

3. Structure of Optical Fiber

4. Analysis techniques
 Ray theory (Fibers with large diameters)
 Step Index Fibers
 Graded Index Fibers
 Electromagnetic Theory (Fibers with small diameters)
 Single Mode Fibers

5. Refractive Index of a dielectric medium
 The ratio of the velocity in vacuum to the velocity of the light in the medium is called
refractive index of the medium
 Light travels faster in vacuum
 Light travels slower in a dense medium
 Refractive index of a dense medium is higher

6. Snell’s law
1 2
1 2
n n
n n
 
 
  
  

7. Total Internal Reflection
n2
n1
> n2
Incident
light
Transmitted
(refracted) light
Reflected
light
kt
TIR
ki
kr
2

1
 c


90
2 

c

 
1
1
2
sin
n
n
c 


8. Total Internal Reflection in Fibers

9. Acceptance Angle

10. Shortest and Longest Paths

11. End of third module
 Thank you