11: Laser, holography and Fibre optics

Example number 11.1, Page number 317

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

#Variable declaration
n1=1.53;   #refractive index of core
n2=1.5;    #refractive index of cladding
lamda=1*10**-6;   #wavelength(m)
a=50*10**-6;    #core radius(m)

#Calculation
NA=math.sqrt((n1**2)-(n2**2));   #numerical aperture(m)
V=((2*math.pi*a)*NA)/lamda;      #normalised frequency
M=(V**2)/2;    #number of guided mode

#Result
print "normalised frequency is",round(V,2)
print "number of guided mode is",round(M)

normalised frequency is 94.72
number of guided mode is 4486.0

Example number 11.2, Page number 317

In [7]:
#importing modules
import math
from __future__ import division

#Variable declaration
n1=1.53;   #refractive index of core
n2=1.5;    #refractive index of cladding
lamda=1*10**-6;   #wavelength(m)

#Calculation
NA=math.sqrt((n1**2)-(n2**2));   #numerical aperture(m)
a=(2.405*lamda)/(2*math.pi*NA);   #core radius(m)

#Result
print "core radius is less than",round(a*10**6,2),"micro m"

core radius is less than 1.27 micro m

Example number 11.3, Page number 317

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

#Variable declaration
NA=0.5;    #numerical aperture(m)
n1=1.54;   #refractive index of core

#Calculation
n2=math.sqrt((n1**2)-(NA**2));    #refractive index of cladding
n=(n1-n2)/n1;     #change in core cladding refractive index

#Result
print "refractive index of cladding is",round(n2,4)
print "change in core cladding refractive index is",round(n,4)

refractive index of cladding is 1.4566
change in core cladding refractive index is 0.0542

Example number 11.4, Page number 318

In [13]:
#importing modules
import math
from __future__ import division

#Variable declaration
NA=0.5;    #numerical aperture(m)
n1=1.48;   #refractive index of core

#Calculation
n2=math.sqrt((n1**2)-(NA**2));    #refractive index of cladding
alpha=math.asin(NA);     #acceptance angle(radian)
alpha=alpha*(180/math.pi);     #acceptance angle(degrees)

#Result
print "refractive index of cladding is",round(n2,3)
print "acceptance angle is",alpha,"degrees"

refractive index of cladding is 1.393
acceptance angle is 30.0 degrees