How to troubleshoot no video output or abnormal picture after device installation and wiring?

When no video output or abnormal picture occurs, troubleshoot in the following order: First, confirm that the pair of devices is used correctly, with the transmitter's receive/transmit wavelengths at 1550nm/1310nm and the receiver's at 1310nm/1550nm, and the wavelengths at both ends must correspond one-to-one; Second, use an optical power meter to check the received optical power and compare it with the receiver sensitivity (better than -32dBm, 1310nm) to confirm whether it is within the usable range; Third, check whether the fiber patch cord end faces are contaminated and whether the FC connectors are tightened; Fourth, verify that the power supply is AC220V or DC-48V; Fifth, confirm that the BNC video port uses a 75Ω coaxial cable and is connected correctly. For daily maintenance, it is recommended to unplug and reinsert the optical ports after power-off, regularly clean the end faces, and re-measure the optical power; if the issue persists, it is recommended to contact the manufacturer's technical support.