Problem: All optical ports cannot be connected, and the indicator lights are not on. Solution: To solve this problem, you can follow these steps: Check if the fiber and optical modules are compatible. Check whether the diagnostic information displays alarms about abnormal transmit or receive power. from transceivers Check “Alarm information” section for warnings, LOS Alarm means no inbound signal, execute display this to check shutdown mode, execute undo shutdown if necessary. 2. Optical modules are widely used in switches, network interface cards (NICs), routers, and other communication devices.