
338 Optical Fiber Communication Systems with MATLAB
®
and Simulink
®
Models
the
carrier,
then
the
coherent
reception
is
of
intradyne
type.
Indeed,
this
difference
has
degraded
the
rst-generation
coherent
reception
systems
for
optical
ber
communications
in
the
mid-1980s.
With
the
digital
signal
processing,
the
phase
carrier
recovery
techniques
can
be
developed
and
overcome
these
difculties.
Heterodyne
reception
would
require
electrical
lter
to
extract
the
beating
channel
information
outside
the
signal
band
and
hence
much
troublesome
as
well
as
cross
talks
between
received
channels.
With
the
bit
rate
and
symbol
rate
now
expected
to
reach
sever ...