Fiber optic internet connection to router not working

A fiber optic connection to a router may fail due to physical cable issues, faulty hardware, or configuration errors, and systematic troubleshooting can restore connectivity.Step 1: Verify Physical ConnectionsEnsure that the fiber optic cable is properly connected from the wall outlet to the Optical Network Terminal (ONT) and that the ONT is powered on. Check for visible damage, sharp bends, or loose connectors in the fiber cable, as even minor bends or contamination can cause signal loss . Clean connectors with lint-free wipes and isopropyl alcohol if necessary.Step 2: Check Router and ONT SetupConfirm that your router supports fiber input, typically via an SFP or WAN port labeled "ONT" or "Fiber" .Connect the ONT to the router using an Ethernet cable from the ONT's LAN port to the router's WAN port.Power on the router and wait for the indicator lights to stabilize (usually 2–5 minutes).Step 3: Inspect Indicator LightsLook for a “LOS” (Loss of Signal) light on the ONT or transceiver. A lit LOS indicates a connectivity issue .Ensure the router's WAN light is active. If it blinks or turns red, the router may not be receiving a valid signal.Step 4: Test Hardware ComponentsSwap suspect transceivers or cables with known-good units to rule out hardware failure .Restart the ONT and router to resolve temporary glitches.Step 5: Verify ConfigurationCheck the router's WAN settings. Some ISPs require static IP addresses, while others use dynamic IP. Incorrect settings can prevent connection .Ensure the router's MAC address is registered with your ISP if required.Access the router's admin panel to confirm IP, gateway, and DNS settings are correct.Step 6: Advanced TroubleshootingUse a fiber power meter or OTDR to measure signal strength. Values outside the typical range (-15dBm to -30dBm) may indicate a problem with the fiber line .If the connection still fails, test a direct connection from the ONT to a computer to determine if the issue is with the router or the ISP's line.Step 7: Contact Your ISPIf all hardware and configuration checks are correct but the connection still fails, the issue may be on the ISP's end, such as network provisioning or line faults . Provide them with details of your troubleshooting steps for faster resolution. By following these steps—checking physical connections, verifying hardware, confirming router configuration, and testing signal strength—you can systematically identify and resolve most fiber optic connectivity issues.