When 40G line or OTU boards work with OLP protection and when happen OLP switch, 40G boards receive AIS signal, dispersion in the line changes, 40G board
starts to search dispersion. Switching time can reach tens seconds.
Comes ODU3_PM_SSF alarm. When start dispersion search appear OTU3_LOF alarm.
To avoid this problem necessary to set dispersion manually. Before necessary to make dispersion search for the main path. Save dispersion value. Then make
OLP switch to the protection path, make dispersion search. Save dispersion value. Then necessary to set manually dispersion value which is in the middle between
the first and second value. Set Fine Tune switch to disable (check attachment) Check perfomance before correction. If it is OK, then no problem. If FEC before
correction is too high, then necessary to correct DCM scheme, set DCM for the longer path before the OLP board to minimize the dispersion difference between the
main and protection paths.
When OLP protection switches, starts dispersion search and OTU3_LOF alarm. Switching time can reach tens seconds.
It is better to not use OLP protecion togever with 40G boards.