Agilent Technologies 8504B - Page 67

FINAL TRIM SIZE : 7.5 in x 9.0 in
P
erforming
Manual
Calibrations
The
precision reectometer
allows
you
to
control
many
of
the
aspects
of
calibrations
.F
or
example
,
you
can
change
the
reection
percentage
(return
loss)
used during
magnitude
calibrations
for
the
standard.
Y
ou
can
also
prevent
the application
of
calibration
data
to
the
measured
data.
A
full calibration
consists
of
two
procedures:

Balance
internal
receiver
.

Magnitude
calibration.
Both of
these
procedures
are
included
in
guided
setups
and
guided
calibrations
.
This section
shows you
how to
run these
procedures
separately
.
Calibrating
pigtailed
devices
As
shown
in
the
guided
setup
procedure,
there are
slight dierences
between
the
steps
used
to
calibrated
devices
with
or
without pigtails
.If
the
device
has
a
pigtail,
during
the
balance
receiver
calibration
the low-reection
termination
is
connected
directly
to
the
TEST
PORT
connector instead
of at
the
end
of
a
cable
.
During
the
magnitude
calibration,
a ber-optic
cable
that
is
the
same
length
as
the
pigtail
is
connected
to
the TEST
PORT
connector
.
Calibration
standards
are
provided
A
magnitude
calibration
consists
of
measuring
a
\standard"
of
known
reection
at
the
end
of
the
TEST
PORT
cable
.
The
instrument
then scales
the
measured
response
to
match
the
amplitude
of
the
\standard"
so
that
the
true
value
is
displayed.
The
ber-optic
cables
supplied
with
the
precision
reectometer
can
be
used
as
calibration
standards
.
This
is because
the cable's
open end
is a
very
accurate
and
repeatable
calibration
standard.
(The insertion
loss at
the front
panel
connection
is
not
taken
into
account.)
The
return
loss of
the ber
end of
these cables
is known
to have
the following
values:
1300 nm
::: :: ::: :: :: ::
::::: :: :: :: ::: :: :: :: :: :::
::::
15 dB (3.16% reection)
1550 nm
:::::::::::::::
:::::::::::::::::::::::::
: 14.7 dB (3.37% reection)
2-20
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