Router connected to fiber optic cable has no signal

No signal on a router connected to fiber optic cable often indicates a physical connection issue, misconfigured WAN settings, or an inactive fiber line from the ISP.

Check Physical Connections

Ensure that the fiber optic cable is securely connected to the Optical Network Terminal (ONT) and the router's WAN port. Inspect the cable for bends, kinks, or visible damage, and verify that connectors are fully clicked in and clean. Dust or oil on connectors can block the light signal, so use lint-free wipes and isopropyl alcohol to clean them if necessary .

Verify Router and ONT Status

• Restart the ONT and router to refresh the connection and force the devices to re-check the signal .
• Check the status lights on both devices. A solid green light typically indicates a proper WAN connection, while red or off lights suggest a problem .
• If your router shows “no WAN connection” or “low fiber,” it may indicate that the signal is not reaching your equipment, which could be a provider-side issue .

Check Configuration

Ensure the router's WAN port settings match your ISP's requirements, such as DHCP or PPPoE. Incorrect settings can prevent the router from establishing a connection even if the fiber signal is present .

Test and Replace Components

If the physical connections and configuration are correct but the problem persists, consider:

• Swapping the fiber transceiver or using a different Ethernet cable between the ONT and router .
• Testing the fiber line with an OTDR or power meter to detect signal loss or breaks .

Contact Your ISP

If all local troubleshooting fails, the issue may be on the provider's side, such as an inactive fiber line or a problem at the street-level connection. Contact your ISP to confirm that your fiber service is activated and properly provisioned . They may need to send a technician to test the line and ONT functionality. By systematically checking physical connections, device status, configuration, and ISP activation, most “no signal” issues with fiber optic connections can be identified and resolved efficiently .