This light shows whether your ONT is getting power. What to check: Make sure the power cable is securely plugged into both the ONT and a working wall outlet. There are no specific requirements for this document. This includes Doppler. System activity and status can be determined through the activity of the LEDs on the switch. A single tricolor LED for each SFP-DD indicates the port status. The LED colors for the switch and their corresponding status indications are as follows ; To Select or change a mode, press the mode button until the desired mode. When I connect the fibre, the 9-port switch shows the fibre link light with the up and down arrows, but the media converter in the other building does not show a fibre link. No Light: The ONT is not receiving. The Optical Network Terminal (ONT) is a crucial device in modern telecommunications, serving as the interface between your home network and the fiber-optic internet connection provided by your Internet Service Provider (ISP).