VeEX FX150, Руководство пользователя

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OTDR Series e-Manual, RevE00 Page 97 of 128
8.2.4.1 Two Point Loss (2-Pt Loss)
The 2-Point Loss mode uses a data point at Marker A and Marker B to calculate the dB level
difference between the two points. Usually the backscatter level value of Marker A is greater
than the level of Marker B and a positive loss measurement is displayed. If the loss value is
reported as a negative quantity, it is termed a “gainer”. Measure loss between two points using
the Loss (2-point) mode (using two markers):
• The data at the bottom of the screen displays: Distance between markers A-B
•
Loss between markers A-B in dB
•
Attenuation between markers A-B
8.2.4.2 Two Point LSA (2-Pt LSA)
To increase the accuracy of a loss or attenuation measurement, a section of the trace
preceding and following the marker A and marker B can be approximated by a straight line. In
this mode, a Least Squares Approximation technique is used to determine the best intercept
values based on the marker positions. The length of these LSA sections is user selectable.
Splice Loss using 2-Point LSA method (MPO)
Select LSA from drop-down list - An approximation line will appear on the screen between
markers. The data box at the bottom displays:
•
Distance between marker A and B (km, miles, feet)
• Level difference in dB
• Attenuation based loss/distance
When using Realtime test mode, use the 2-Point LSA method to stabilize loss
values.