The SNMP trap that is generated when an interface transitions from an error to normal state because the alarms/warnings are below the threshold. snTrapOpticalMonitoringError would have been earlier generated when the interface transitioned to the error state. The first varbind, snAgGblTrapMessage, will have a detailed message on the cause of event. The second varbind, ifIndex, points to the affected interface originating this event. If an event does not have associated port, or has multiple associated ports, then ifIndex will have maximum value 0x7ffffff.