ywguo
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Hi Raj,
The jitter in serial data communication are put into two categories, random jitter (RJ) and deterministic jitter (DJ).
DJ has several sub-types, duty cycle distortion (DCD), data dependent jitter (DDJ), periodic jitter.
DCD is usually caused by the unsymmetrical rise and fall edge of the driver. In your case, a 40Gbps optical driver. You need to run 010101... pattern to measure it. A data pattern, saying 0000101111 is not suitable because DDJ also affects on the rise/fall times.
DDJ is also called ISI. It is inter-symbol interference in fact because the channel is band-limited. So a rise/fall edge succeeding a long 0/1 bit stream is more slow. For pseudo-random binary stream (PRBS), run transient simulation and plot its eye diagram, the rise edges are not coincident. And the same for all falling edges.
Periodic jitter is usually caused by low frequency sinusoidal interference on supply voltage. It caused the jitter varies periodically.
Yawei
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