EXFO OTDR 2 - Manual (Page 98)

Analyzing the Results Manually
90 OTDR
Getting Section Loss and Attenuation
Getting Section Loss and Attenuation
The least-square approximation (LSA) method measures the attenuation
(loss over distance) between two points by fitting a straight line in the
backscatter data between markers A and B. The LSA attenuation
corresponds to the difference in power ( dB) over the distance between
two points.
The LSA method, when compared to a two-point method, gives an average
measurement and is more reliable when there is a high level of noise.
However, it should not be used if an event such as an echo appears
between the two markers.
A-B LSA loss: the loss of the event bordered by the markers A and B is
obtained by fitting a straight line to the backscatter data between these two
markers.
The event is then obtained by the reduction in power (dB) over the
distance between the two markers, as calculated from the slope of the
fitted line.
A-B LSA loss
a
b