Before connecting the cable, locate the fiber optic port on your router. It's typically labeled as “Fiber,” “ONT,” or “WAN” (Wide Area Network). Fiber optic modem (ONT): Most fiber connections require an Optical Network Terminal (ONT), provided by your ISP. The ONT is linked to your router or gateway using an Ethernet cable. This can be done in two ways: Underground Installation – Fiber cables are placed in conduits underground, offering better protection from weather and physical damage.