MTP-200 Series User’s Manual
Shineway Technologies, Inc. - 64 -
12.4 Measure Attenuation (2-point and LSA method)
2-point method measures the attenuation between Marker A and B calculated by all the loss
over the distance between Marker A and B (Unit: dB/Km). Use only these two points to
calculate and the average value does not exist.
LSA (least-squares approximation) method uses linear regressions that is applied to the
backscatter before and after an event (Between Marker A and B) to estimate the attenuation
in the backscatter resulting from the event’s loss. LSA method only measures the amplitude
(decibel) change between the crossing points of the trace with Marker A and B.
Compared to 2-point method, LSA method is more accurate because it is less sensitive to
trace noise and suitable for measuring splice attenuation. However, LSA method should not
be applied to measure attenuation when there are reflection events between Marker A and B.
Measure attenuation:
1. Click {Markers} label in OTDR main interface to show Marker A and B.
2. Place Marker A and B at different points on trace.
3. Zoom in the trace to adjust marker position when necessary.
4. Check 2Pt. Atten. (2-point attenuation) and LSA Atten. (LSA attenuation) values,
as shown in Fig. 12.5.
Fig. 12.5 View attenuation
There should not be any event between Marker A and B when measuring attenuation with
2-point method.
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