# Ch-4 Optical Fiber Transmitter¶

## Example 4.21 Page no 486¶

In [6]:
from __future__ import division
from math import sqrt, pi

# Calculation of wavelength seperation between longitudinal modes.

#Given data
lamda=0.85#                   # Wavelength
n1=3.6#                        # Refractive index of GaAs
L=200*10**-6#                   # Length of cavity

# Wavelength seperation between longitudinal modes.
lambda1=((lamda)**2)*(10**-12)/(2*n1*L)#
lambda1=lambda1*10**9#

#Displaying results in the command window
print"Wavelength seperation = %0.1f nm**2"%(lambda1)#

Wavelength seperation = 0.5 nm**2


## Example 4.22 Page no 486¶

In [7]:
# Computation of overall external efficiency

#Given data
eg=1.43#            # Bandgap energy
v=2.5#              # Electrical supply Voltage
nd=0.18#            # Optical efficiency of laser diode

# Computation of overall external efficiency
ne=(nd*eg/v)*100#

print"Overall external efficiency = %0.0f %%"%(ne)#

Overall external efficiency = 10 %


## Example 4.23 Page no 486¶

In [8]:
# Calculation of overall external efficiency of a Laser diode

#Given data
eg=1.43#            # Bandgap energy
v=2.5#              # Voltage applied
nd=0.30#            # Optical efficiency of laser diode

## Overall external efficiency
ne=(nd*eg/v)*100#

print"Overall external efficiency = %0.0f %%"%(ne)#

Overall external efficiency = 17 %