Symptom
During the project deployment or maintenance, it is probable that an SDH board on the SDH equipment reports an R_LOF alarm when the SDH board is interconnected with a tributary board, such as TOM or TQX, on the client side of the OptiX OSN 6800 equipment. In most cases, the problem is not caused by a hardware fault.
Cause analysis
The OptiX OSN 6800 system is not a synchronous communication system, and therefore cannot provide high-quality clock signals that are synchronous networkwide. In this case, when the OptiX OSN 6800 forcibly emits lights or actively transmits pseudo random binary sequence (PRBS) signals, the interconnected SDH equipment receives signals that are not strictly framed by the clock. As a result, the SDH equipment fails to detect the A1 and ** bytes, and reports an R_LOF alarm. The problem occurs in the following scenarios:
l The service configuration in the OptiX OSN 6800 system is correct. The local OptiX OSN 6800 receives SDH services on the client side and the remote OptiX OSN 6800 does not receive any service on the client side. In this case, the SDH board on the SDH equipment interconnected with the local OptiX OSN 6800 reports an R_LOF alarm.
l Both the local OptiX OSN 6800 and remote OptiX OSN 6800 receive SDH services on their client sides. The cross-connection configuration, however, is incorrect. In this case, both the SDH boards on the SDH equipment interconnected with the local OptiX OSN 6800 and remote OptiX OSN 6800 report the R_LOF alarms.
l Both the local OptiX OSN 6800 and remote OptiX OSN 6800 receive SDH services on their client sides. The cross-connection configuration is correct. The optical path on the WDM link, however, is abnormal. In this case, both the SDH boards on the SDH equipment interconnected with the local OptiX OSN 6800 and remote OptiX OSN 6800 report the R_LOF alarms.
l Both the local OptiX OSN 6800 and remote OptiX OSN 6800 receive SDH services on their client sides. The cross-connection configuration is correct. The timeslot allocation of the electrical cross-connections, however, is abnormal. In this case, both the SDH boards on the SDH equipment interconnected with the local OptiX OSN 6800 and remote OptiX OSN 6800 report the R_LOF alarms.
l The optical module on the SDH board of the SDH equipment or the optical module on the local OptiX OSN 6800 is faulty. In this case, the SDH board on the SDH equipment interconnected with the remote OptiX OSN 6800 reports an R_LOF alarm.
Procedure
Interconnect a tributary board on the OptiX OSN 6800 with an SDH board on the SDH equipment. Check for the fault according to the preceding scenarios when the SDH board reports an R_LOF alarm.
Result
The problem is resolved.
