EXFO PSO-100 Series Optical Sampling Oscilloscopes - Manual (Page 125)

Measurement Definitions
Optical Sampling Oscilloscope 117
Pulse Width
Pulse Width
The pulse width measurement is only possible for RZ pulses. It can be used
both for eye diagrams and pulses without data modulation. From a thin
horizontal histogram at the 50 % threshold between the one and zero levels
the mean crossing points determine the pulse width.
Contrast Ratio
The contrast ratio (CR) is only defined for RZ data as the ratio between the
one level and the level between the pulses, that is
.
Similarly as for the ER, the CR depends on the accuracy of the DC offset
level. It is therefore important to calibrate the dark level before
measurement.
Pulse width
CR P
one
P
contrast
⁄ =
One level
Contrast level