EXFO PSO-100 Series Optical Sampling Oscilloscopes - Manual (Page 121)

Measurement Definitions
Optical Sampling Oscilloscope 113
Rise Time and Fall Time
Rise Time and Fall Time
The rise time is calculated from horizontal histograms according to the
figure below.
The time delay between the times where the slope transits through the
10 % and up to the 90 % thresholds determines the rise time. In the same
way, the fall time is calculated as the time delay between the transit times
through the 90 % level down to the 10 % level. The 10-50-90 % thresholds
can be changed to 20-50-80 % in the Measure menu under Thresholds.
Extinction Ratio
The extinction ratio (ER) of an eye diagram is simply the ratio between the
one level and the zero level. The accuracy of the ER can be dominated by
with which the zero level is measured. The DC offset in the instrument
electronics in turn can affect this. It is therefore important that the dark
level (P
dark
) is calibrated before the ER measurement. Calibrating the dark
level is done in the Utilities menu. The ER is defined as:
Histograms
Rise time
10 %
90 %
ER
P
one
P
dark
–
P
zero
P
dark
–
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