# Chapter 15 : Fibre Optics Sensors And Instrumentation¶

## Example15_1,pg 470¶

In [2]:
# find increamental phase

import math
#variable declaration
n1=1.48                #refractive index of fibre
mu=0.2                 #poisson's ratio
p=2.2*10**2            #pressure applied
lam=690.0*10**-9       #laser beam wavelength
Y=2.2*10**11           #young's modulus

#Calcaulation
delphi=((4*math.pi*n1*mu*p)/(lam*Y))

#Result
print("increamental phase:")
print("delphi = %.6f rad"%delphi)
#Answer is slightly different
increamental phase:
delphi = 0.005391 rad

## Example15_2,pg 474¶

In [15]:
# find additional length travelled

import math
#Variable declartion
r= 9                        #radius of fibre loop
a=math.pi*((r/2)**2)        #area of fibre loop
Q=1.0                       #linear velocity(cm/s)
Co=3*10**8                  #velocity of light(cm/s)

#Calculations
delL=((4*a*Q)/(Co))           #additional length travelled

#Results
print("delL = %.1f * 10^-8 cm"%(delL*10**8))
#Answer is not matching with book
delL = 67.0 * 10^-8 cm

## Example15_3,pg 512¶

In [2]:
# find interacting length

import math
#Variable declaration
#(Po1/Po2)=1/2 and Po1+Po2=3Po2=Pi
Po2byPi=1.0/3.0                        #(Po2/Pi)

#Calculations
kL=math.acos(math.sqrt(Po2byPi))       #k->coupling coefficient
L=kL                                   #L=kL/k L->interacting length

#Result
print("interacting length:")
print("L = %.4f/k"%L)
# answer is slightly different than book
interacting length:
L = 0.9553/k

## Example15_4,pg 512¶

In [30]:
# wavelength suitable for laser light

import math
#Variable declaration
We=7.6*10**-5               #speed od gyro
L=490.0                     #length
c=3*10**8                   #speed of light
delphi=7.69*10**-5          #phase shift
d=0.094

#Calculations
lam=((2*math.pi*L*d*We)/(c*delphi))            #wavelength of laser light

#Result
print("wavelength of laser light:")
print("lam = %.f *10^-9 m"%(lam*10**9))
#Answer isslightly different than book
wavelength of laser light:
lam = 953 *10^-9 m

## Example15_5,pg 513¶

In [32]:
# find rate of change of RI wrt T

import math
#Variable declaration
#(delphi/delT)=(2pi/lam)(n*(delL/delT)+L*(deln/delT))=(deln/delT)
lam=635.0*10**-9                 #wavelength of light beam
delphi=139.0                     #phase angle
delL=0.49*10**-6                 #change in length
n=1.48                           #R.I of fibre

#Calculations
k=((lam*delphi)/(2*math.pi))-(delL*n)       #//k=(deln/delT), rate of change of R.I w.r.t T

#Result
print("rate of change of R.I w.r.t T:")
print("k = %.2f * 10^-6/°C"%(k*10**6))
# Answer is nnot matching to book
rate of change of R.I w.r.t T:
k = 13.32 * 10^-6/°C