The router connected via fiber optic cable cannot access the internet

If your router connected via fiber optic cable cannot access the internet, the issue is often due to missing ISP activation, incorrect router settings, or improper ONT/modem connections.Check Physical ConnectionsEnsure that the fiber optic cable is properly connected to the Optical Network Terminal (ONT) or fiber modem, and that the ONT is powered on. Then, connect the ONT to your router's WAN port using an Ethernet cable. Avoid bending or damaging the fiber cable, as it is fragile, and wait a few minutes for the ONT lights to stabilize before testing the connection .Verify ISP ActivationMany fiber connections require the ISP to activate the service for your router or ONT. Some routers, like the FRITZ!Box, may need to be unlocked or registered with the ISP before internet access is granted. Check if your ISP has provided a PPPoE username and password or other credentials, as these are often required for the router to establish a connection .Router ConfigurationAccess your router's admin panel via a browser using its IP address (e.g., 192.168.1.1).Confirm that the WAN/Internet settings match the type of connection your ISP uses (Dynamic IP, Static IP, or PPPoE).If using PPPoE, enter the username and password provided by your ISP.Ensure the router's firmware is up to date, as outdated firmware can prevent proper connectivity .Test and TroubleshootReboot both the ONT and router.Connect a device directly to the ONT to verify if the internet works without the router. If it does not, the issue may be with the ISP or ONT configuration .Check the router's status page to see if it detects the fiber connection. If it shows “interrupted” or “unknown,” contact your ISP for activation or troubleshooting .Additional ConsiderationsSome ISPs provide a customer portal where you can find connection credentials or activate your service.If multiple devices cannot access the internet, the problem is likely upstream (ISP or ONT) rather than the router itself .Ensure that your router is fiber-ready or compatible with GPON/FTTH connections; not all routers can directly handle fiber input . By systematically checking the physical setup, verifying ISP activation, and configuring the router correctly, most fiber optic connectivity issues can be resolved. If problems persist, contacting your ISP for support is often necessary.