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Why is the value of OI4 output jitter more than the ITU-T standard

Publication Date:  2012-07-24 Views:  97 Downloads:  0
Issue Description
Test analyzer: ANT-20E Test item: OI4 output jitter of single station ITU-T standard: STM-4 B2 (250KHz~5MHz) output jitter less than 0.10UI Test result: output jitter about 0.170UI
Alarm Information
no alarm
Handling Process
1.Before I test output jitter of optical interface, we first confirm that test connection is correct and then I set the analyzer configuration correctly . It includes signal structure ,clock tracing and test items. Notes: Don? generate jitter from Tx of analyzer. So after this procedure I get the result of output jitter is 0.178, but the test method is correct. 2.Then I consider maybe OI4 have problem about output jitter?so I test other three OI4 boards in different sites, but the result is also failed and more than 0.10UI. 3.So I think it is the problem of OI4 first. But I heard the result of output jitter of OI4 is about Jp-p=0.15UI (B1) and Jp-p=0.080UI (B2).But the results of this time are about Jp-p=0.22UI (B1) and Jp-p=0.17UI (B2),they are 0.08UI more than the normal result. Now why don? I doubt the analyzer? So I do this work as below: Loop back analyzer, and then get the result of output jitter, however it also have jitter , about 0.08UI , so I know why we get the bigger output jitter because of the jitter of SDH analyzer, if We decrease the jitter of ANT-20E from actual result(0.17-0.08=0.09UI) .so that result is passed.
Root Cause
We can process this test problem through test method, board performance, test environment and test equipment.
Normally we used SDH analyzer to test our SDH equipment, so we are afraid of suspecting the analyzer, we always suspect equipment and test method. So I suggest we first check SDH analyzer using loop back when we are testing output jitter