Agilent Technologies 83446A User Manual
Bit-Error-Ratio
T
est
Optical
ber
su ers
from
chromatic
dispersion,
which
causes
light
at
di erent
wavelengths
to
travel
through
the
ber
at
slightly
di erent
velocities
.
Since
the
linewidth
of
a
laser
is
not
in nitesimally
narrow
,
the
di erent
wavelength
components
will
not
all
arrive
at
the
end
of
a
long
length
of
ber
at
the
same
time
.
This
tends
to
atten
and
spread
out
fast
risetime
pulses
,
leading
to
intersymbol
interference
.
This
e ect,
called
dispersion
power
penalty
,
is
de ned
as
the
di erence
in
minimum
detectable
power
level
with
and
without
dispersion.
Example
of
measuring
dispersion
power
penalty
of
single-mode
ber
The
Agilent
83446A/B
,
in
conjunction
with
the
Agilent
71604B
error
performance
analyzer
or
similar
BERT
,
can
measure
the
dispersion
power
penalty
of
an
optical
ber
when
used
with
a
particular
laser
source
.
Since
dispersion
power
penalty
depends
on
the
spectral
characteristics
of
the
laser
source
,
it
is
important
that
the
test
laser
be
representative
of
the
laser
to
be
used
in
the
actual
system.
3-3