EXFO PSO-100 Series Optical Sampling Oscilloscopes - Manual (Page 71)

Setting up and Using the Optical Sampling Oscilloscope
Optical Sampling Oscilloscope 63
Using Masks
Using Masks
Mask testing is a procedure commonly used to verify that a transmitter
complies with certain standards. The test is done in an eye diagram, where
masks are placed in three regions: in the center of the eye, above the logic
one, and below the logic zero level. Samples in these regions are
unacceptable and referred to as mask hits or mask violations.
You can also activate a mask margin, which is slightly larger (a certain
percentage) than the original mask to see the tolerance area within the eye
diagram.
You can see at the bottom of the application the results from the mask test,
including the total number of samples, the number of hits in the mask and
in the margin, etc.
The mask is only placed in one eye period, so if for example four eyes
periods are shown in the application, it will take longer time to acquire a
certain number of samples in the mask test. Therefore, EXFO recommends
to visualize one eye period.