Chapter 3: Optical Sources

Example 3.1,Page number 67

In [2]:
import math

#given

Pin=1;          #microW
W=15;           #in degree
NA=math.sin(W*math.pi/180);
NAA=0.26;       #NA=0.2588190 which is rounded off
C_c=(NAA)**2;
print"Coupling coefficient is ",C_c;
Pf=C_c*Pin;
print"Power coupled into fiber ",Pf*1000,"nW\n";

Coupling coefficient is  0.0676
Power coupled into fiber  67.6 nW

Example 3.2,Page number 67

In [4]:
import math

#given

n=0.02;         #in percentage
W=20;           #in degree
Vf=1.5;         #in Volts
If=20;          #in mAmps
Pin=If*Vf;
print"Power coupled into fiber ,Pin = ",Pin,"mW";

Po=n*Pin;
print"Output Power of the optical source is ",Po,"mW";

#from nc=20 degree
C_c=(math.sin(W*math.pi/180))**2;
Pf=C_c*Po
print"Optical power coupled into fibre is ,Pf = ",round(Pf*1000,4),"microW";

Power coupled into fiber ,Pin =  30.0 mW
Output Power of the optical source is  0.6 mW
Optical power coupled into fibre is ,Pf =  70.1867 microW

Example 3.3,Page number 68

In [6]:
import math

#given

tr=10;          #in nsec
BW=0.35/tr/10**-9;
print" Maximum operating bandwidth is ",BW/10**6,"MHz\n";    #divided by 10**6 to convert answer in MHz

 Maximum operating bandwidth is  35.0 MHz

Example 3.4,Page number 70

In [11]:
import math

#given

T=1;    #Air
NA=0.3;
n0=1;
#x=y;
print"for step index :A=infinite";
#for infinite alpha
#nc=T*(NA/n0)^2*(x/y)^2*(A/(A+2))
nc=T*(NA/n0)**2*(1)**2*1;         # A/(A+2)=1 for A=infinite

print"Coupling Coefficient,nc = ",nc*100,"percent";

print"for graded index :A=2";
A=2;
#n_c=(T*(NA/n0)^2*(A+(1-(y/x)^2))/(A+2))
n_c=(T*(NA/n0)**2*(A+(1-(1)**2))/(A+2))       #x/y=1
print"Coupling Coefficient,nc = ",n_c*100,"percent";

for step index :A=infinite
Coupling Coefficient,nc =  9.0 percent
for graded index :A=2
Coupling Coefficient,nc =  4.5 percent

Example 3.5,Page number 71

In [15]:
import math

#given

T=1;  #Air
NA=0.3;
n0=1;
A=2;
#y=0.75x;
print"for step index :";
#for infinite alpha
#nc=T*(NA/n0)^2*(x/y)^2*(A/(A+2))
nc=T*(NA/n0)**2*(1/0.75)**2*A/(A+2);             #y/x=0.75
print"Coupling Coefficient,nc = ",nc*100,"percent";

print"for graded index :A=2";
A=2;
#n_c=(T*(NA/n0)^2*(A+(1-(y/x)^2))/(A+2))
n_c=(T*(NA/n0)**2*(A+(1-(0.75)**2))/(A+2))       #y/x=0.75
print"Coupling Coefficient,nc = ",round(n_c*100,4),"percent";

for step index :
Coupling Coefficient,nc =  8.0 percent
for graded index :A=2
Coupling Coefficient,nc =  5.4844 percent

Example 3.6,Page number 72

In [20]:
import math

#given

#calculate Tf
If=85;           #in mAmps
Vf=2.5;          #in Volts
Ta=25;           #in deg C

#calculate Tj
W=150;           #in C/W for hermetric led
Pd=If*Vf;
Tj=Ta+W*Pd/1000;
print"Value of Tj is ",Tj,"deg C";

TF=8.01*10**12*math.e**-(8111/(Tj+273));
print"Value of TF is ",round(TF,4),"deg C";

#calculate RF
BF=6.5*10**-4;               #from table
QF=0.5;                     #from table
EF=1;                       #from table
RF=BF*TF*EF*QF*1/10**6;
print"Value of RF","{0:.3e}".format(RF);
print"Value of MTBF is ","{0:.3e}".format(1/RF),"hours";

#Answer in book is misprint in last line

Value of Tj is  56.875 deg C
Value of TF is  167.9406 deg C
Value of RF 5.458e-08
Value of MTBF is  1.832e+07 hours

Example 3.7,Page number 74

In [25]:
import math

#given

#calculate Tf
If=120;          #in mAmps
Vf=1.8;         #in Volts
Ta=80;           #in deg C
#calculate Tj
W=150;          #in C/W for hermetric led
Pd=0.5*If*Vf;
Tj=75+W*Pd/1000;
print"Value of Tj is ",Tj,"degree cel";
TF=8.01*10**12 *math.e**-(8111/(Tj+273));
print"Value of TF is ",round(TF,4);
#calculate RF
BF=6.5*10**-4;               #from table
QF=0.2;                     #from table
EF=0.75;                       #from table
RF=BF*TF*EF*QF*1/10**6;
print"Value of RF is ","{0:.3e}".format(RF);
print"Value of MTBF is ","{0:.3e}".format(1/RF),"hours";

Value of Tj is  91.2 degree cel
Value of TF is  1704.4223
Value of RF is  1.662e-07
Value of MTBF is  6.018e+06 hours