Optical Transceiver Troubleshooting: Before You Replace the SFP
Check optics, compatibility, power and fiber before declaring a transceiver failed.
Read the diagnostics before reseating anything
Digital diagnostics can show transmit power, receive power, temperature, voltage, bias current, alarms, and module identification. Capture those values before reseating or replacing the optic so useful evidence is not lost.
Compare local transmit power with far-end receive power and vice versa. Normal transmit with poor remote receive suggests path loss more strongly than a dead transmitter.
Verify compatibility and operating mode
Check speed, wavelength, reach, connector type, FEC, encoding, and platform support. Two optics can physically fit and still be inappropriate for each other. Tunable systems also require the intended wavelength or channel configuration.
Review both ends rather than assuming the newly installed side is the only possible problem.
Use known-good substitution as a controlled test
Replace one component at a time, record the module identity, and compare diagnostics immediately. If the fault stays on the same fiber direction after a known-good optic is installed, shift attention to the jumper, patch panel, span, or receiver path.
Do not ignore marginal optics. A link can remain up with very little margin and create intermittent errors long before it goes hard down.