Fiber optic internet offers high-speed connectivity. The router connects to a fiber optic modem or Optical Network Terminal (ONT). Fiber to fiber media converters can convert between single-mode fiber (SMF) and. 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. In this guide, we'll walk you through how to. Fiber network design is only possible with appropriate networking equipment, such as fiber optic cables, connectors, termination boxes, splicing equipment, and active components (for example, switches and routers).