FTTH Network HOW-TO Test and Measurements

How to get a better OTDR Trace during FTTx PON network testing


OTDR Price is getting economical recently, how to get a good test trace from an cost effective OTDR is critical, the following lists is an instruction about how to get good test result.

1. Select the right pulse width, by selecting a longer or shorter Pulse Width, you can control the amount of backscatter level coming back, and the dead zone size. High the pulse width, large the dead zone, and less accuracy of the testing result. For a cascading splitter PON network, too wide pulse width might directly ignore the second splitter, if the distance among splitter is too short, however, if the pulse width is too narrow, there might be too much noisy of the trace after splitter. The following table is an example about pulse width and measurement distance during fiber network testing.

2. Measurement Range, Its recommend to have the measurement trace about1/3 to 1/2 of the OTDR display. If wrong measurement range selected, you will get compressed trace or stretched trace

3. Dirty, damaged or incompatible connectors, resulting in a large reflection and curved trace at the beginning of the trace. Inspect and clean connectors. Make sure both connectors are of the same type and endface finish (PC, UPC, or APC). Use connector colors to identify PC/UPC vs. APC.

Source from: http://www.tarluz.com/test-equipment/tips-improving-otdr-trace-quality/