61
Taking Standard Loss Measurements
Measuring the Return Loss
8
Press
C
ALIBRATE
.
9
Press
D
ISP
–>P
REF
. The power reflected from the open end of the
optical output and received by the optical head is stored as the
reference power.
If there is no value
displayed any more, the
optical head has not been
zeroed. Refer to page 31 in
section 1.6 “Getting
Started” to find out how to
zero the head.
10
Wind the optical output fiber cable close to the open end in seven
tight loops around a pen.
This almost eliminates the reflection from the open fiber end.
The remaining optical power is caused by so-called parasitic
reflections within the test setup. It should be as small as
possible (below –50 dBm).
11
Press
D
ISP
–>P
PAR
. The current value is stored as the parasitic
power.
12
Unwind the optical output fiber cable.
13
Press
P
REVIOUS
to return to the measurement screen.
The display shows the open-end reflection.
You now are ready to attach your DUT.
Figure 3-5
Return Loss Calibration Display
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