Triple-Play Service Deployment

Appendix A: PON Reflectometer Trace Analysis
Fault localization and attenuation estimation
After locating the distance where the deviation begins to appear,
the location of the fault can be identified.
Eventually the fault can be associated with an event recorded in
the reference table. Due to the mixing of multiple branches, fault
attenuation cannot be directly calculated from the attenuation
deviation between the two curves (Figure A.9).
Figure A.9 Identifying the location and attenuation of a fault
Using a pattern simulator, though, a virtual attenuator can be
inserted into the affected branch and the attenuation can be
increased until the same deviation from the reference pattern is
achieved. This technique allows for an approximation of the
attenuation level of the fault.
Accuracy and Limitations of the Method
Because this type of analysis involves measurements, it is
necessary to point out its accuracy and limitations. As far as
accuracy is concerned, the main source of error lies in the reality of
the simulator models and data entry uncertainties. For example,
optical splitters reverse and forward parameters may need to be
entered. The fiber backscatter coefficient deviations add some
uncertainty on the attenuation estimation and could be
integrated into the theoretical formula.
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