
43Optical Fibers: Geometrical and Guiding Properties
the
wave
propagation
of
the
signal
enveloped
via
the
nonlinear
Schrodinger
equation.
Theevolution
of
slow
varying
complex
envelopes
A(z,
t)
of
optical
pulses
along
a
single-
mode
o
ptical
ber
i
s
g
overned
b
y
t
he
n
onlinear
S
chrodinger
e
quation
(
NLSE)
[
22]:
∂
∂
+ +
∂
∂
+
∂
∂
−
∂A z t
z
A z t
A z t
t
j
A z t
t
A z t( , )
( , )
( , ) ( , ) ( ,α
β β β
2 2
1
6
1 2
2
2
3
3
))
( , ) ( , )
∂
= −
t
j A z t A z t
3
2
γ (2.72)
where
z
i
s
t
he
s
patial
l
ongitudinal
c
oordinate
α
a
ccounts
f
or
ber
a
ttenuation
β
1
indicates DGD
β
2
and β
3
represent second- and third-order factors of ber CD
γ is
t
he
n
onlinear
c
oefcient
This equation is described in