Optical Backscatter Reflectometer 4600 95
User Guide
The Reference Trace Processing Parameters should be changed only to correct a
situation in which good devices are failing because of mismatched features caused
by random but acceptable variations between devices.
Impo
rta
n
t
Ideally, many devices should be tested before a
Reference Trace is settled upon, to make sure that the
Processing Parameters being used will result in a
consistent set of features for every good device tested. It
should then be unnecessary to modify the Reference
Trace later.
Press Cancel to exit the Parameter Specifications window without modifying the
Reference file.
Setting the Maximum Device Length
Sometimes there may be trailing noise present in a trace after all of the actual
features. Differences in this noise level may cause the LightPath Analysis software
to conclude that a trace has failed, even though all of the desired features are within
the correct limits. In these cases, it is advantageous to specify a Maximum Length
beyond which no features will be compared.
To specify this value, select Setup > Data Processing Parameters from the main
menu. Verify that C:\LPA_Data\golden is still the selected Reference Data Folder
at the top of the Parameter Specifications window (Figure 6-4 on page 83). In the
Device Length section at the lower left, check the Use Maximum Length checkbox
and change the value of Maximum Length to 5.0. Press Apply to re-evaluate the
current trace (still device3.obr) without re-saving the Reference. The trace will be
reprocessed but will only display up to the last feature within 5.0 meters.
Note
Although the Maximum Length is set to 5.0, the last Peak
ends at just over 2 meters. The software omits the trailing
Fiber segment, showing only the data up to the end of the
last Peak or Drop.
The Trace Comparison window (Figure 6-10 on page 92) will also show only the
features occurring before the Maximum Length.
The Maximum Length value can also be modified through the Tolerance
Specification window (Figure 6-8 on page 88) Select Setup > Feature-Specific
Tolerances from the main menu. Click in the Use Maximum Length checkbox just
To Next Page
