JDS Uniphase RX3 Series, Руководство пользователя

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points that is caused by the fiber, all connections and the DUT, for example, the area within
the dashed line in Figure 12.
Figure 12: Measuring Backreflection
6. If necessary, terminate the fiber for BR
0
again, just before the DUT, to eliminate the
backreflection caused by the fiber and all connections before the DUT.
7. Press the BR
0
key. The key lamp lights to indicate that the BR
0
function is on.
8. Release the termination. The meter now displays the backreflection of the DUT only.
9. To make a measurement at a second wavelength, repeat steps 2 to 8.
The small amount of reflections that BR
0
represents can be polarization sensitive, and multiple
reflections can cause interference effects that make the reflections very sensitive to
temperature. To ensure accurate backreflection measurements below -25 dB, perform the BR
0
measurement frequently or before each measurement.
Backreflection Accuracy and Range
The absolute accuracy of backreflection measurements made with the RX3 meter depends on
the level of backreflection to be measured.
The backreflection measurement is restricted by the BR
0
level. The meter can measure
backreflection levels 15 dB below BR
0
, to a maximum of -40 dB (for multimode). For example, if
BR
0
is -20 dB, the maximum backreflection range is -35 dB.
An asterisk (*) is displayed near the range limit (last 5 dB of range). The asterisk emphasizes
that the setup and measurement procedures described in this manual must be followed carefully
to ensure accurate results.
Absolute accuracy specifications depend on the accuracy of the meter calibration; a calibration
check needs to be performed periodically (see the
Calibrating the Meter section).
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