Triple-Play Service Deployment

Appendix A: PON Reflectometer Trace Analysis
Displayed attenuations on a PON reflectometer trace
There are two types of attenuation on a multi-branch
backscattered signal.The first type, Ac, is located at the splitter.The
second type, AFEi, is located where fiber branch ‘i’ ends,
corresponding to a fiber end. These attenuations are closely
dependent on the adjacent fiber parameters (backscatter
coefficients) as well as the splitter parameters (forward and
reverse insertion losses).
In order to more fully understand the analysis, a simplified version
of the theoretical formula is defined. It requires the following
assumptions:
1. The different fibers connected to the splitter have very similar
characteristics, including bidirectional symmetry behaviors,
backscatter coefficients, and attenuation.
2. The splitter has the same characteristics for both directions.
Taking into account these assumptions, the different types of
attenuation are calculated by the following formulas:
Ac = 5xlog(m) + E.L.
AFEi = 5xlog[(m-i+1)/(m-i)]
where E.L. is the excess loss of the splitter, m is the number of
outputs, and i is the analyzed branch.
Analysis Method of PON Reflectometer Trace Analysis
This example uses a 1:8 splitter with the same assumptions as in
the theoretical method. A standard OTDR is used to obtain the
signature of the link. The analysis method requires a learning
acquisition phase. This phase uses an optical network OTDR
measurement simulator. This innovative simulator, developed by
JDSU, can be used with both point-to-point and point-to-multipoint
networks. In addition to classical fiber, connector, splice, and
attenuator simulation, the software algorithms integrate n to m
splitter synthesis based on an attenuation behavior formula
similar to the calculations of Ac and AFEi.
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