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I am a newbie learning SONET technologies.I have read about SONET ,got a basic idea regarding synchronization,frame format,layers ,standards etc .I am finding hard to understand the concepts of pointers in SONET. Googled many things ,but not have a clear cut idea.Would love to know the following, 1)pointers working concept 2)How the addition of pointers can compensate for jitter , clock differences and other errors.

Any help is really appreciated, Thanks in Advance

sudeep
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1 Answers1

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On fast/long links, timing can be lost (I'm not discussing deeper into line codes (instead, I'm using the simple line code below) and timing recovery, because it is not needed to answer your question); think of it this way:

tx'd:            1   0   1   0   1   1   0   0   1   0   1   0
                ----    ----    --------        ----    ----
sample time:     ^   ^   ^    ^   ^   ^    ^   ^   ^    ^   ^
rx'd              1   0   1    0   1   1    0   0   1    1   0
                                                         ^
                                            a "slip"; should be 1

--The pointer adjustment corrects this by telling the receiver to adjust when the sample is taken.

Andrew
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