# Chapter 5 : Fibre Optics¶

## Example number 1 , Page number 90¶

In [1]:
#importing module
import math
from __future__ import division

#Variable declaration
n1=1.5                  #core refractive index

#Calculations
thetac=math.asin(n2/n1)
NA=(n1**2-n2**2)**0.5
im=math.asin(NA)

#Result
print"Critical angle= %2.2f" %math.degrees(thetac),"degrees"
print"numerical aperture= %1.3f" %NA
print"acceptance angle= %2.3f" %math.degrees(im),"degrees"

Critical angle= 78.52 degrees
numerical aperture= 0.298
acceptance angle= 17.367 degrees


## Example number 2 , Page number 91¶

In [2]:
#importing module
import math
from __future__ import division

#Variable declaration
n1=1.6                #core refractive index
NA=0.2                #Numerical aperture

#Calculations
NA=(n1**2-NA**2)**0.5

#Result
print"refractive index of cladding= %1.3f" %NA

refractive index of cladding= 1.587


## Example number 3 , Page number 91¶

In [3]:
#importing module
import math
from __future__ import division

#Variable declaration
n1=1.6                 #core refractive index

#Calculations
NA=(n1**2-n2**2)**0.5
im=math.asin(NA)

#Result
print"numerical aperture= %1.3f" %NA
print"Acceptance angle= %2.2f" %math.degrees(im),"degrees"  #The answer in the textbook is mathematically incorrect

numerical aperture= 0.252
Acceptance angle= 14.61 degrees


## Example number 4 , Page number 91¶

In [4]:
#importing module
import math
from __future__ import division

#Variable declaration
delr=12*10**-3         #fractional refractive index change
NA=0.22                #Numerical aperture

#Calculations
n1=NA/math.sqrt(2*delr)
n2=n1-(n1*delr)

#Result
print"refractive index of core material= %1.2f" %n1
print"refractive index of cladding material= %1.2f" %n2

refractive index of core material= 1.42
refractive index of cladding material= 1.40


## Example number 5 , Page number 92¶

In [5]:
#importing module
import math
from __future__ import division

#Variable declaration
NA=0.2                 #Numerical aperture
n0=1.33                #refractive index

acceptance angle= 8.6 degrees