The simplest way to test an SFP transceiver is with the FiberLert™ live fiber detector, which lights up and beeps when placed in front of an active fiber or port. There are no specific requirements for this document. This includes Doppler. This article describes how to troubleshoot malfunctioning or flapping optical modules. Remove the SFP module from the slot. Clean any dust on the fiber patch or patch panel. When. Quick reference for interpreting Digital Optical Monitoring (DOM) values on fiber optic modules (SFP, SFP+, QSFP, etc), identifying acceptable, caution, and unacceptable levels, and general issue troubleshooting examples.