HP 83480A User Manual

Eye, Mask and Eyeline Mode Measurement Tutorials
Making Eye Diagram Measurements
Measuring extinction ratio
For HP 83480A only
Extinction ratio is the ratio of the most prevalent high logic level to the
most prevalent low logic level over one bit interval. As the logic low level
approaches 0 volts or watts, the extinction ratio can become very high. Any
residual oset signals within the instrument can become signicant if their
magnitude approaches the logic 0 level. A more accurate measurement of
extinction ration would be:
E
xtinction
r
atio
per
cent
=
100

P
base
0
P
dar
k
P
top
0
P
dar
k

Because
of this
relationship
,
part
of
the
procedure
for
performing
an
extinction
ratio
measurement
is
to
do
a
dark calibration.
You
are
instructed
to
turn
o
the
laser
so
that
the
instrument's
internal oset
can
be
measured.
After
the
calibration
is
performed,
data
for
the
database
will begin
to
acquire
.
Some
of
the
data
will
be
measured
points
acquired
while the
laser
is
still
o,
therefore
,
the
laser
should
be
turned
on,
allowed to
stabilize
,
and
then
the
instrument's
display
should
be
cleared
to
have
a
valid
database
.
The
extinction
ratio
measurement
is
dened
using
the
measurement
database
as
the
mean
high
level
over
a
windowed
portion
of
the
eye
.
This
window
is
nominally
the
middle
20%
of
the
eye
.
F
or
more
information
on
dening
your
measurements
,
refer
to
the
Dene
Measure menu
in Chapter
10 of
this
manual.
Marker lines The marker lines delineate the measurement boundaries. The X markers
dene the measurement window. Only data taken inside this window is
used to determine the measurement results. The Y markers dene vertical
boundaries of the measurement.
The
extinction
ratio
measurement
is
made
by
rst determining
a
window
in
the
center
20%
of
the
eye
.
All data
points
in
that
measurement
window
are
used to determine the logic level 1 and 0.
5-10

HP 83480A Specifications

General

Brand	HP
Model	83480A
Category	Measuring Instruments
Language	English