EXFO FTB-7000 OTDR Series for FTB-500 - Manual (Page 206)

Analyzing the Results Manually
192 OTDR
Getting Event Loss (Four-Point and Least-Square Approximation)
To get event loss:
1. From the main window, go to the Graph tab and press the Measure
button.
2. In the Measurements section, press Loss. Markers a, A, B and b
appear on the graph.
3. Zoom in and position marker A at the end of the linear area preceding
the event to be measured. For more information, see Using Zoom
Controls on page 137 and Using Markers on page 187.
4. Position submarker a at the beginning of the linear area preceding the
event to be measured (must not include any significant events).