
380 Optical Fiber Communication Systems with MATLAB
®
and Simulink
®
Models
9.4.7.6 Population Inversion Factor Modeling
•
N
1
simulation.
R
ecall
t
he
t
hree
s
tate
po
pulations
a
nd
t
he
a
ssumption
t
hat
N
3
is zero. The relation
b
etween N
1
and N
2
is then N
1
= N
total
− N
2
(Figure 9.26).
•
N
sp
simulation (Figure 9.27)
A
ccording
t
o
t
he
po
pulation
i
nversion
f
actor
e
quation,
N
1
would equal N
2
. This
w
ould
l
ead
t
o
t
he
r
esult
a
pproaching
i
nnity.
T
herefore,
t
he
[
if
s
tatement]
c
ould
l
imit
t
he
r
esult
t
o
u
nder
1
0.
A
lso,
t
he
po
pulation
i
nversion
f
actor
w
ould
b
e
g
reater
t
han 10 in practice.
Input ×
SUM
+Lift time
ASE photons
Discrete-time
integration
EDFA dynamic
gain
1–exp( ...