An ONT, or Optical Network Terminal, is a device that converts fiber network signals from light into electric signals that can be used by a Wi-Fi router. An ONT is an interface between the fiber optic network that carries optical signals and the devices that use electrical signals, such as routers, telephones, or computers. An ONT is similar to a modem for fiber internet, as it allows the devices to communicate with the internet service provider (ISP) and access the internet.