
246 Optical Fiber Communication Systems with MATLAB
®
and Simulink
®
Models
Two
arms
of
the
dual-drive
MZM
modulator
are
biased
at
V
π
/2 and −V
π
/2 and driven with
data
and
data. Phase-shaping driving sources can be a periodic triangular voltage source
in
case
of
linear
MSK
generation
or
simply
a
sinusoidal
source
for
generating
a
nonlinear
MSK-like
signal,
which
also
have
the
linear
phase
trellis
property
but
with
small
ripples
introduced
in
the
magnitude.
The
magnitude
uctuation
level
depends
on
the
magnitude
of
the
phase-shaping
driving
source.
High
spectral
efciency
can
be
achieved
with
tight
ltering of the driving signals before modulati ...