A fiber router, or fiber optic router, is a router that is specifically equipped to support fiber Internet. Fiber offers a super fast Internet connection and does so by sending pulses of infrared light through an optical fiber cable. An ONT (Optical Network Terminal) is used in fiber internet to convert light signals into data, while a modem is used in cable or DSL connections to modulate and demodulate signals. Its main function is to translate. An ONU is a terminal device in a fiber-to-the-home (FTTH) network. Also called “fiber boxes,” fiber ONTs are typically. Often called a fiber modem by customers, the ONT performs a similar function to traditional modems but operates on entirely different principles.