Exfo FTB-7000 OTDR for FTB-200 v2 Uživatelský manuál stáhnout pdf (Strana 287)

Maintenance

OTDR 273

Verif ying Your OTDR

To measure the event and attenuation dead zones:

1. Connect 2 km of fiber directly to the OTDR port. Use the shortest pulse

width and distance range possible.

³ Ensure that the OTDR port and connectors are correctly cleaned.

³ Ensure that the fiber settings are accurate (IOR, Helix factor,

and RBS).

2. Measure the length (E) of the first reflection at 1.5 dB from the

maximum, as shown below. This is the event dead zone.

3. Measure the distance (A) between the beginning of the reflection and

the point where the trace returns to the backscattering level with a

0.5 dB uncertainty, as shown below. Use A and B markers in the

Measure pane. This is the attenuation dead zone.

If the results exceed the “maximum permitted specification” (refer to the

calibration certificate that came with your product), performance will be

affected. A damaged output connector may be the cause.

The reflectance of the output connector should be below –35 dB to attain

an adequate dead zone. If reflectance is greater than –35 dB

(for example, –20), the incorrect dead zone will be the result of a bad

connection. If this is the case, carefully clean the connector. If the problem

persists, change the output connector. If the problem remains even after

changing the output connector, return the OTDR to EXFO.

Note: This does not affect the precision of the distance or loss measurements.

1.5 dB

0.5 dB

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Exfo FTB-7000 OTDR for FTB-200 v2 Uživatelský manuál Strana 287