# 12: Fibre Optics¶

## Example number 12.1, Page number 263¶

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

#Variable declaration
NA=0.39;    #numerical aperture
delta=0.05;     #refractive index of cladding

#Calculation
n1=NA/math.sqrt(2*delta);      #refractive index of core

#Result
print "refractive index of core is",round(n1,3)
refractive index of core is 1.233

## Example number 12.2, Page number 264¶

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

#Variable declaration
n1=1.563;          #Core refractive index
n2=1.498;          #Cladding refractive index

#Calculation
delta=(n1-n2)/n1;    #fractional index change

#Result
print "fractional index change is",round(delta,5)
fractional index change is 0.04159

## Example number 12.3, Page number 264¶

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

#Variable declaration
n1=1.55;          #Core refractive index
n2=1.50;          #Cladding refractive index

#Calculation
NA=math.sqrt(n1**2-n2**2);    #numerical aperture

#Result
print "numerical aperture is",round(NA,2)
numerical aperture is 0.39

## Example number 12.4, Page number 264¶

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

#Variable declaration
n1=1.563;          #Core refractive index
n2=1.498;          #Cladding refractive index

#Calculation
NA=math.sqrt(n1**2-n2**2);    #numerical aperture
theta0=theta0*180/math.pi;    #acceptance angle(degrees)

#Resul"
print "acceptance angle is",round(theta0,2),"degrees"
acceptance angle is 26.49 degrees

## Example number 12.5, Page number 265¶

In [6]:
#importing modules
import math
from __future__ import division

#Variable declaration
n1=1.53;          #Core refractive index
n2=1.42;          #Cladding refractive index

#Calculation
thetac=thetac*180/math.pi;    #critical angle(degrees)

#Resul"
print "critical angle is",round(thetac,2),"degrees"
critical angle is 68.14 degrees

## Example number 12.6, Page number 265¶

In [8]:
#importing modules
import math
from __future__ import division

#Variable declaration
n1=1.6;          #Core refractive index
n0=1.33;         #refractive index of air
n2=1.4;          #Cladding refractive index

#Calculation
NA=math.sqrt(n1**2-n2**2)/n0;    #numerical aperture
theta0=theta0*180/math.pi;    #acceptance angle(degrees)

#Resul"
print "acceptance angle is",round(theta0,2),"degrees"
print "answer in the book varies due to rounding off errors"
acceptance angle is 35.62 degrees
answer in the book varies due to rounding off errors

## Example number 12.7, Page number 265¶

In [9]:
#importing modules
import math
from __future__ import division

#Variable declaration
n1=1.5;          #Core refractive index
n2=1.3;          #Cladding refractive index

#Calculation
delta=(n1-n2)/n1;    #fractional index change

#Result
print "fractional index change is",round(delta,3)
fractional index change is 0.133

## Example number 12.8, Page number 265¶

In [10]:
#importing modules
import math
from __future__ import division

#Variable declaration
n1=1.55;          #Core refractive index
n2=1.6;          #Cladding refractive index
theta1=60*math.pi/180;     #incident angle(degrees)

#Calculation
x=n1*math.sin(theta1)/n2;
theta2=theta2*180/math.pi;    #refraction angle(degrees)

#Result
print "refraction angle is",round(theta2,2),"degrees"
refraction angle is 57.03 degrees

## Example number 12.9, Page number 266¶

In [11]:
#importing modules
import math
from __future__ import division

#Variable declaration
n2=1.3;          #Cladding refractive index
delta=0.140;    #fractional index change

#Calculation
n1=n2/(1-delta);     #Core refractive index

#Result
print "refractive index of core is",round(n1,2)
refractive index of core is 1.51

## Example number 12.10, Page number 266¶

In [12]:
#importing modules
import math
from __future__ import division

#Variable declaration