346 Keysight M8000 Series of BER Test Solutions User Guide
6 Setting up Analyzer
If the Analyzer attempts to synchronize on the incorrect detect word, the
BER will be unacceptably high, and, if automatic synchronization is
selected, the Analyzer attempts another re-sync.
The detect word on which the Analyzer attempts to re-sync is chosen
strictly by chance. So if there are two instances of the detect word in the
pattern, the Analyzer has a 50% chance of selecting the correct one.
The more instances of the detect word exist in the pattern, the higher are
the chances for incorrect synchronization. The software attempts in any
case to identify a 48-bit pattern that occurs as seldom as possible in the
pattern. For very large patterns, this can unfortunately take a very long
time, and the software ends the search if it expects that it would take
longer to find an adequate detect word than it would to attempt to
synchronize. If the search for a detect word is ended, the most unique
detect word identified is used.
Patterns must always be synchronized in order to do accurate BER testing.
If patterns are out of alignment by just one bit, errors can be as high as
50% (5E-1) for PRBS patterns, and 100% (1E+0) for custom patterns.
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