Step 1 Replace the optical fiber and check the alarm. The fault persists.
Step 2 Replace the optical module of the port on the storage controller. The fault persists.
Step 3 Exchange the optical fibers that connect the NAS engine to ports 00 and 02 of controller A. It is found that port 2 that generates the alarm restores to normal but port 00 generates the alarm of abnormal optical signal receiving.
Step 4 Determine that the HBA port of the NAS engine is faulty.
Step 5 Replace the HBA of the engine. The fault is rectified.