EXFO PSO-200 Optical Modulation Analyzer - Manual (Page 270)

Measurement Definitions
262 PSO-200
Measurements for Eye Diagrams
Pulse Width
The pulse width measurement only applies to RZ formats. From a thin
horizontal histogram at the 50 % threshold between the one and zero levels
the mean crossing points determine the pulse width. It is measured in the
magnitude graph of the signal.
Eye Width
The eye width is a measurement of the horizontal opening of the eye. It is
defined as:
where the mean crossing points, T
cross
, and horizontal standard deviations
are measured from the histograms in the eye diagram.
Pulse width
T
rise,center
T
fall,center
EW T
cross2
3 
cross2
–   T
cross1
3 
cross1
+   – =

cross
Eye width