VeEX OTDR FX150+ Series, Руководство пользователя

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OTDR Series e-Manual, D07-00- 076P -RevD00 Page 89 of 109
4. Position center marker on the event’s rising or falling edge. You can use the rubber keypad
to place the marker exactly, if needed.
5. Position the first two markers on a section of backscatter preceding the event and position
the last two markers on a section of backscatter after the event ensuring that enough
pre/post backscatter is used to make an accurate measurement. Markers A and B should
be placed on the left and right but as close to one another as possible. The whole transition
section should stay between them.
All five markers can be moved independently or moved as a group
simultaneously depending which marker is active
.
The sections between the first two markers and the last two markers are approximated by
straight lines (LSA) whilst the value of event loss is defined by the position of the center
marker.
The result box at the bottom of the screen displays:
• Spl (km, meters, miles or feet) - distance of center marker
•
Loss of the event in dB based on the pre/post LSA sections and center marker
•
Reflectance in dB if event is reflective
7.7.6 Reflectance Measurement
Reflectance is measured in -dB (negative decibels). A smaller negative value (-65dB) indicates
a smaller reflection whereas a larger negative value (-45dB) indicates a larger reflection.
Larger reflectance will appear as a higher spike on the trace.
1. Select trace for measurement (if multiple traces are displayed on screen). The trace to be
measured can be selected using the green arrow in the trace overview window.
2. Select Reflectance (Refl) from the drop-down list at the bottom of the display.
3. Expand the trace horizontally and vertically (using Zoom Controls) to display the reflection
correctly. The entire reflection should be displayed including a small section of the trace
preceding and following the event.
4. Place the left marker on the event’s rising edge. The right marker is placed on the peak of
the reflection.
The result box at the bottom of the screen displays:
•
Distance of A cursor (reflection) from Start of test fiber
•
Distance of B cursor (top of reflection) from Start of test fiber
•
Distance between markers A->B
•
Reflection for this even (-dB)