The fiber optic cable does not plug directly into a standard home router because the signal type must be translated. The fiber line terminates at the Optical Network Terminal (ONT), which is typically supplied and installed by the internet service provider. This. When issues like signal loss, slow speeds, or intermittent connectivity arise, systematic troubleshooting is key. This guide will walk you through diagnosing and resolving common fiber network issues efficiently. Why Do Fiber Networks Fail? Despite their robustness, fiber networks can fail due to:. An Ethernet cable will connect your equipment to the fiber terminal. CenturyLink has three main fiber-compatible modems.