Disconnect the LAN cable from the router's WAN port. To identify why your fiber internet isn't working, it's important to establish where the connection problem is. 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. Problems with fiber optic internet can range from signal attenuation to optic signal loss to equipment malfunctions. By shedding light on these common fiber internet problems and offering insights into preventative measures and advanced troubleshooting steps, we aim to empower network. Heck, sometimes you can get back up to speed just by tightening the coaxial cable on a cable modem. CenturyLink has three main fiber-compatible modems.