The router only has one fiber optic indicator light on

If your router shows only one fiber optic light on, it usually indicates that the PON (Passive Optical Network) connection is active, but other functions like LAN or internet connectivity may not be fully established.Understanding the LED IndicatorsPOWER Light: Should be solid if the router is powered on. If off, check the power cable and outlet .PON Light: A solid PON light indicates the fiber connection is active and the optical signal is within normal levels (-20 dBm to -27 dBm). A blinking PON light may indicate abnormal signal levels .LOS (Loss of Signal) Light: Normally off. If on or blinking red, it signals a fiber disconnection, dirty connector, broken patch cord, or no signal from the ISP .LAN/WLAN Lights: Should flicker when devices are connected and active. If off, it may indicate no device is connected, a faulty cable, or disabled Wi-Fi .Common Causes for Only One Light OnRouter is powered but not fully connected: Only the power or PON light may be on while LAN or internet lights remain off .Fiber signal issues: Dirty connectors, loose fiber cables, or a cut in the fiber line can prevent full connectivity .ISP or account issues: Even if the PON light is on, the internet may not work if the ISP service is suspended or there is an outage .Hardware or configuration problems: Incorrect router settings or a malfunctioning WAN port can prevent other lights from turning on .Troubleshooting StepsCheck connections: Ensure the fiber cable is securely connected to the router and the ONT (Optical Network Terminal), .Reboot devices: Power cycle both the router and the ONT to restore connections .Inspect cables and connectors: Clean fiber connectors and replace any damaged cables .Verify LAN connections: Connect a device directly to the router using a CAT-5e or CAT-6 cable to test LAN functionality .Check router settings: Access the router's web interface to confirm WAN or PON settings are correct. Some routers may require forcing the internet port negotiation speed to 100 Mbps full duplex if only one LED is active .Contact ISP support: If the problem persists, your ISP can check for external network issues or account-related problems . By following these steps, you can determine whether the single light indicates normal operation or a connectivity problem and take appropriate action to restore full network functionality.