
113Overview of Modeling Techniques for Optical Transmission Systems
The design of DCF and DFF is more complicated than that of SSMF as it involves a multi-
cladding/core structure (see Figure 4.8) compared to the simple step-index prole of SSMF [18].
4.3.3 Dispersion Length
An
important
parameter
that
governs
the
effects
of
ber
CD
on
optical
pulses
is
the
dis-
persion
length
L
D
. This length corresponds to the distance at which a pulse broadens by
one-bit
interval
[19,22].
For
high-capacity
and
long-haul
transmission
employing
external
modulation,
L
D
can be estimated as [22]:
L
D R
D
=
⋅
10
5
2
(4.20)
where
R is
t
he
b
it
r
ate
(
Gb/s)
D
i
s
i
n
p
s/(nm
·
km)