If there is a red light, please check the yellow fiber patch cable with green tips connected to the back of the unit. You may also need to verify that the outlet is receiving power. ”. If you're still having issues with the Optical/Config/PON Light flashing, being off, or showing red, please contact us to report this so we can take a look. By following these instructions, you should be able to troubleshoot and potentially resolve the issue with your Optical Light. What Does the LOS Light Indicate? The LOS light on your router indicates the status of your internet connection to the Internet. A router showing a red light can mean different things, like a service outage, misconfiguration, or loose connection, all of which can lead to a broken internet connection.