Kingfisher KI23400 Series, Руководство по эксплуатации и техническому обслуживанию

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AUTOTEST TWO-WAY OPERATION
KI23400/KI27400 UM-2
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33 -
To set the reference, enter relative mode, then hold down [Set Ref] for
3 seconds until the instrument beeps finish. The main display will go
to approximately 0 dB, and the reference value is displayed on the left
side of the display. The length test will also be set to 0.
If measuring ORL, there are additional ways of optimising ORL test
accuracy, which are covered in the ORL section of the manual.
To exit Two-Way Autotest, on any of the two connected instruments,
select [Home] or disconnect patch lead for more than 8 seconds, and
wait a few seconds for the other unit to drop out.
Length Measurement
Length measurement is a part of the two-way Autotest function, on a
pair of instruments that have the length measuring option.
Length is measured by time-of-flight on one fiber, which is affected by
the fiber refractive index. The RI values used in the instrument are:
SM: 1550 nm 1.4668
1310 nm 1.4567
MM: 1300 nm 1.4835 850 nm 1.4734
These RI values are close enough for almost all applications.
Instruments fitted with either a 1550 nm laser or 1300 nm LED will use
only these two wavelengths for length measuring.
If a fiber with a very different RI is used, the length can be recalculated
e.g. Actual = Measured x (instrument RI / actual RI)
Length measurement is zeroed when a reference is taken, so the test
cord length is excluded from the measurement.
This function is reliable and unaffected by optical line reflections, PC /
APC connector type etc.
Measuring range is determined by optical loss, e.g. the receiver
sensitivity.
The theoretical absolute accuracy of this measurement is of the order
of 0.01% ±1 meter, ±any IOR inaccuracy. Towards the attenuation
limit of the length test, absolute length accuracy will reduce slightly.
However, practical cable length measuring accuracy is usually limited
by many other factors such as:
•
Cable length marking accuracy (typically about 1 %)
•
Fiber length is greater than cable length (often about 2 %)
•
As-built dimensions are different to planned dimensions
•
Various lengths of fiber get left looped in place, etc.
•
Calibrated reference cable lengths of < 0.5 % accuracy do not
exist in practice.
“Left-to-right” loss (dB)
“Right-to-left” loss (dB)
Length measurement
Average loss (dB)
of the 2 directions
Figure 1. LCD display of Two-Way Autotest data/result
Test status
indicator for a
wavelength.
PASS
Overall test result