You can't directly connect a fiber optic cable to your router. You need an intermediary device. This comprehensive guide combines industry standards with field-tested practices to ensure you achieve a rock-solid. To connect your fiber optic cable to a router, ensure you have the following: Fiber optic modem (ONT): Most fiber connections require an Optical Network Terminal (ONT), provided by your ISP. The fiber line terminates at the Optical Network Terminal (ONT), which is typically supplied and installed by the internet service provider.