I suppose you mean the shifting in an EFM pattern on a laser output of a CD/dvd player?
Just use a good analogue scope, and measure the width of the shifting pattern on the rising portion of the signal. Most players have this test point labeled for test purposes.
This is the eye diagram. My problem is that high level is greater than low level, then the rises doesn`t break. Why happend it? wich is the jitter in this signal? Thanks