Only the fiber optic cable is lit up on the router

If only the fiber optic (PON) light is lit on your router, it usually indicates that the router is receiving a fiber signal but is not establishing a full internet connection.Understanding the Fiber (PON) LightThe PON or fiber light on your router or Optical Network Terminal (ONT) indicates that the device is receiving a signal from your ISP's fiber network . A solid green light typically means the fiber connection is active, but if other lights such as Internet, LAN, or Wi-Fi are off, it suggests that the router is not distributing the internet signal to your devices .Common CausesEthernet or internal connection issues: The router may not be properly connected to the ONT via Ethernet, or the internal routing may be misconfigured .Router or ONT configuration errors: Incorrect IP settings, firmware bugs, or misconfigured network parameters can prevent full connectivity .Hardware problems: Faulty routers, ONTs, or fiber transceivers can cause the internet light to remain off even if the fiber signal is present .ISP-side issues: Sometimes the fiber signal is active, but the ISP's network is down or your account is not fully provisioned .Troubleshooting StepsPower cycle devices: Turn off both the router and ONT, wait 30 seconds, then turn them back on to reset connections .Check fiber and Ethernet cables: Ensure the fiber cable is securely connected and free from bends or damage. Verify the Ethernet cable between the ONT and router is properly seated .Inspect router settings: Log into your router's admin panel to check for IP assignment, DHCP status, and firmware updates .Test with another device: Connect a computer directly to the ONT to see if the internet works, which helps isolate whether the issue is with the router or the ISP .Contact your ISP: If the above steps do not resolve the issue, your ISP can check for external network problems or re-provision your connection .Key TakeawayA lit fiber optic light alone indicates that the physical fiber connection is active, but the lack of other lights or internet functionality points to configuration, hardware, or ISP issues. Following the above troubleshooting steps usually identifies the cause and restores full connectivity.