Diagnosing Fiber Cabling Faults
Diagnosing OTDR Test Failures
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Table 10-4. Diagnosing Faults on OTDR Traces (cont.)
amd163.eps
Top figure: Ghost after the cabling end
These are not listed in the event table and generally do not indicate a fault in the cabling.
Bottom figure: Ghosts in the middle of the cabling
Ghosts occurring in the middle of the cabling are listed in the event table, along with the source
of the ghosts. These can be caused by the following:
•
A dirty connector
•
A highly-reflective connector
•
A UP or UPC connector mated to an APC connector
•
A connector that is not seated properly.
A poorly-seated connector usually shows significant loss, as shown in the example. A connector
with the wrong type of polish can also cause strong reflections that result in ghosts.
Ghosts caused by hidden events may not be identified as ghosts in the event table.
Tip: On traces with multiple ghosts, only the first ghost may be identified in the event table. You can
usually determine that other reflections are ghosts because they occur at multiples of distances to
connectors and they show almost no loss. Multiple ghosts from the same source are spaced
equally apart.
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