Nortel Networks OPTera Metro 3500 - Manual (Page 51)

Operation, administration, and maintenance (OAM) features 2-13
Planning and Ordering Guide—Part 1 of 2 NTRN10AN Rel 12.1 Standard Iss 1 Apr 2004
BLSR Line Protection Oscillation Control
OPTera Metro Release 12.0 introduced a line protection oscillation control
mechanism for BLSR systems. If 3 signal failures (SF) are detected on a line
within 12 seconds of each other the line protection oscillation control
mechanism is activated and protection will be in a lockout condition for 12
seconds. The OPTera Metro 3500 will raise an “Auto Switch Complete -
Oscillation” alarm. The lockout condition is released only after 12 seconds
have elapsed without a signal fail (SF) transition.
This feature is not provisionable and is always on.
BLSR single span fiber cut scenario
A fiber cut - and any other cause of signal degradation or signal failure on a
span - causes a BLSR autonomous switch. A fiber degradation scenario is
described in the following example. See
Figure 2-4 on page 2-17 to Figure
2-11 on page 2-24 to see the following order of events after a signal
degradation between Node 3 and Node 4 occurs.
Note: The following steps correspond to the step numbers in the graphics.