There are several reasons for “no light” issues: incompatible SFP module, incorrect connection, SFP module not powered on, or bad SFP. Incompatible SFP: Please check the compatibility of your optical transceiver with your equipment. Incorrect connection:. This is a high-level summary of the situation, but it's really strange (and YES, I have swapped the transmit and receive). If the optical module is installed on a GE port, run the display interfaceGigabitEthernet x/x/x command to view port information when the optical module. Common incompatibilities between modules and devices include: The transceiver is not recognized by the device; it is unresponsive when inserted, and the device does not retrieve transceiver information. Upon inserting the transceiver, the device displays errors such as "Not Supported," "Unknown,". We're having some problems: 1. 165a on 12v power supply, but no image is displayed. Despite their robust design, these modules can experience failures due to environmental stress, contamination, or incompatibility.