There was a fiber cut between an OSN 2500 (node A) and an OSN 3500 (node B). The node B could not connect to NM, because the configuration of both nodes was NP_Chain and the management was brought through DCC. The services in node B were down. After fiber provider reported the restoration of the alarm, a R_LOF alarm was reported in line board of node A, and the services remained affected.
R_LOS, R_LOF, IN_PWR_FAIL
After confirm the correction of the fiber problem it is advisable to do the following:
1.Check whether the fiber is incorrectly connected.
2.Check whether the received optical power at the local station is proper.
3.If the optical power was higher than the overload value of the board (for this case for example), use fixed attenuators to adjust the right value of optical power.
4.If the alarm (R_LOF) persists, check whether the launched optical power at the opposite station is within the specified value range.
5.Perform remote and loop-backs and set byte J0 to check continuity of the path.
6.If you check the optical power through NM and the value remains the same, even if there is a physical disconnection or new fixed attenuators in the reception, possibly there is a failure in the optical module.
7.Replace faulty board
Due to the link had a very long distance, BA2 with SL16 (very long distance) boards were installed in both ends of the link between node A and B. The gain of the BA2 board was approximately 14 dBm, using as Booster Amplifier. When the fiber link was restored, the optical power exceeded the overload of the of the N1SL16 board, due to the fiber provider by mistake performed a physical loop 250m away of the node A.Because the node B had not connection with NM it was not possible to verify precisely the status of the link.
When performing loopbacks be aware of the overload value of the boards in order to avoid failure in the receiving port.
If there is a failure in a link with optical amplifiers (BA2 for example), close the laser in case of fiber cut.
When using amplifiers it is advisable to use protection features suchs as ALS (Automatic Laser Shutdown) and IPA (Intelligent Power Adjustment)
In order to avoid lost of NM when there is a fiber cut in a NP_Chain configuration, it is advisable to provide a IP connection to each member of the chain.