During system test when we turn off the laser from NE2 to NE3 the clock signal switching didnt show the expected operation.
In normal condition clock signal must to change to NE4 to NE3 direction. If fiber between NE2 � NE3 is restored the signal (active clock priority) still working in the NE4 to NE3 direction until “wait to restore time” is finished and after that (normally 5 min) signal clock will change to normal (original) condition (NE2 to NE3).
If during restore time (before finished the 5 min) the fiber between NE4 � NE3 is opened and the fiber between NE2 � NE3 is working normally, signal clock priority have to change to “Internal state” (suppose three state west, east and internal), when “wait to restore time” is finished the signal will change to NE2 to NE3 direction (first clock priority).
In this case when the fiber between NE2 � NE3 is opened the clock signal change to NE4 to NE3 but when the fiber NE2 � NE3 is restored, automatically the clock signal change to NE2 to NE3 direction.
Check the attachment
We done the same test but this time customer close the laser in DWDM side. Now we receive the R_LOF alarm and the clock signal switching was normal.
We suggest to customer check the DWDM trasnponder because all them are not working in the same way.
Additional if they can not change the OTU configuration, we can configure AIS like a optional trigger for clock signal switching.
During a fiber broken NE3 have to receive R_LOF signal in slot8 (from NE2) whit this alarm the either services and clock signal have to switch normally.
But during these test, the laser was shut off in SDH side, by this reason DWDM (other vendor) transfer not in all case the R_LOF alarm, most of times transfer only MS_AIS.
MS_AIS is a multi-section protection trigger and by this reason services was swiched normally. But MS_AIS is not a default trigger for clock swiching and when we opened the fiber (actually we close the laser in DWDM side), The clock quality of board in slot 8 changed from PRC to DNU and NE3 starting to receive the clock signal in slot 11. Later, when we restore the path in slot 8 again we receive PRC and the signal change automatically to slot 8.
Is important remark here, clock signal have not to work in the same way than service; clock signal, in services switching when the fiber is restored and the second fiber (now work fiber) is open before finished the "wait to restore time" services switiching automatically to the original path, like that services are protected.
But with clock signal, if second fiber (now work fiber) is restored before "wait to restore time" is finished, clock signal is transfer to third priority (in our case "internal priority") and when "wait to restore" is finished the clock priority will transfer to first clock priority
Check if the trigger for Regeneration section are OK, if not check if you have some equipment in middle for example DWDM and if they insert the right alarms.
Remember clock signal switching has by default his trigger in Regeneration section, AIS are optional trigger.