SFP modules are very robust and don't easely present any failures. Still, if there is a customer reporting that their SFP is not working and you want to verify if its in fact the SFP or other component please follow the next steps:
Step 1. Prepare two switches that are SFP compatible. Make sure the network speed between switch and SFP is the same (e.g. 1Gbps SFP switch + 1Gbps SFP).

Step 2. Insert a pair of SFP module to each switch (a transmitters and receiver).

Step 3. Connect both switches together using fiber optic cables.

Step 4. Connect a camera to one switch and a PC to the another switch.

Step 5. Use the Shepherd application to see if the camera can be found in the network.
If the camera cannot be found you can try:
- Changing the fiber optic cables connected between switches
- Change one of the SFP modules connected to the switch (with a new one)
- Change SFP module port (you will need to unisntall the module and install in the next port to it if available)
Note: If the switch used is a managed switch (e.g https://www.vivotek.com/aw-gev-267a-370), it has a function that allows you to check the status of the SFP connected on the switch, you can find more information in the switch user’s manual.
If after the test it was found that the issue is related with the SFP module it will need to be send back to VIVOTEK HQ for repairs.