Which device is responsible for terminating a fiber connection?

An Optical Network Terminal (ONT) is the correct choice for terminating a fiber connection because it serves as the interface between the fiber optic network and the customer's premise. The ONT converts optical signals, which are transmitted over fiber optic cables, into electrical signals that can be used by the devices within a home or business, such as computers, phones, and routers.

The role of the ONT is crucial in Fiber to the Home (FTTH) or Fiber to the Premises (FTTP) setups, where fiber optic lines run directly to a building and require a conversion point for the data to be utilized. The ONT typically handles not just internet data but also voice and video services, depending on the provider's offerings.

The other devices listed, such as routers, cable modems, and DSL modems, are designed for different types of connections—typically for copper-based connections (like coaxial or twisted-pair cables). Routers facilitate the distribution of internet traffic within a local area network, while cable and DSL modems are used to connect to broadband services provided via coaxial cable or telephone lines, respectively. They do not terminate fiber optics; hence, they would not serve the function of an ONT.