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SONET_Usr.bk Page 193 Wednesday, December 13, 2000 11:11 AM
Selecting and Using "OTHER" Features
PRBS Polarity Control (Option 003 only)
PRBS Polarity Control (Option 003 only)
Description
You can select PRBS patterns with NORMAL or INVERTed polarity from the
TRANSMITTER and RECEIVER windows.
The definition of NORMAL and INVERTed differs between ITU-T O.150 and
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23
common practice usage in the United States of America for 2
-1 and 2
-1 PRBS
patterns.
The PRBS polarity control allows the user to select which definition is used on the
TRANSMITTER and RECEIVER windows.
The ITU-T O.150 standard specifies that the NORMAL or default for all PRBS
patterns should be inverted. This will produce a longest string of n-1 consecutive
n
zeros in a 2
-1 PRBS pattern. Therefore selecting INVERT with an ITU-T pattern
n
will produce a longest string of n-1consecutive ones in a 2
-1 pattern.
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The ITU-T definition also applies in the US, except for 2
-1 and 2
-1 PRBS
patterns. Through common practice, NORMAL indicates that the PRBS pattern is
non-inverted. Therefore when the 'US' PRBS polarity control is enable and
NORMAL is selected for these two patterns on the TRANSMITTER, a longest
string of n-1 consecutive ones is produced. The pattern has to be INVERTed in
order to produce a longest string of n-1 consecutive zeros.
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