Fluke OF-500-01 OptiFiber Technical Reference Handbook page 190

OF-500 OptiFiber Certifying OTDR
Technical Reference Handbook
Loss is negative.
•
The connections to the tester were disturbed after referencing.
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The fiber ends were dirty during referencing.
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There was a kink in a reference test cord during referencing.
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The connectors were not properly aligned during referencing.
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Some other problem caused a bad reference value.
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If loss is negative, set the reference again and retest the cabling.
A known length of cable measures too long or too short.
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The wrong fiber type is selected on the Cable tab in Setup.
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The index of refraction needs adjustment. Change n on the Cable tab in Setup.
7-38
Table 7-10. Diagnosing Loss/Length Test Failures (cont.)