Even if the fiber optic internet connection is the fastest there is, there may be slowdowns or problems to be solved

Slow fiber

With the new fiber optic connection technologies we always expect a very high download speed, so that we can manage all the new Internet services without problems. Unfortunately, the scenario is not always so “idyllic”: even with fiber optic connections we can run into unexpected slowdowns, endless page loads, blank or half-loaded web pages and downloading of the largest files with a much higher time than the average. . Fortunately, most problems are easily solved checking the modem settings or applying small tricks to restore the correct functioning of the line.

Problems with the latest connection technologies can involve various devices and various scenarios, not all of which can be replicated in an absolute sense (many problems are so unique that they do not have an answer). As far as possible we will try to show you how to solve problems with slow optical fiber, focusing in particular on mixed copper fiber (also called FTTS, FTTC, FTTN or VDSL), which is the technology most subject to interference or technical problems.

READ ALSO -> Best Optical Fiber: check coverage and offers

Modem Problems

When the fiber optic connection makes a tantrum the first suspect is certainly the modem: in fact, it takes very little to find yourself with a slow or unstable connection, despite all the Megabits available. The most common problems with modems are:

  • Slow Wi-Fi frequency: if we use the 2.4 GHz frequency of Wi-Fi we will often get slowdowns, especially if there are many nearby networks with the same frequency. To solve we pass most of the devices on the rete a 5 GHz, using gods if necessary Wi-Fi repeaters.
  • Too many simultaneous connections: even with the optical fiber we can suffer slowdowns in downloads, especially if several devices download large files at the same time. To solve we always try to download one large file at a time (since it will take a few seconds) and optimize the internal Wi-Fi network to prioritize connection to devices that require more bandwidth (for example consoles or Smart TVs).
  • Resource saturationModems also have CPU and RAM as core internal components. If we saturate the internal resources (for example with online gaming) all connected devices will slow down, losing any advantage in having the optical fiber. To avoid these problems it is better to choose high performance modem.
  • Temporary error: The modem can also go crazy or suddenly overheat. To solve these problems we try to restart it or leave it off for 2-3 minutes.

Most of the problems described above can be solved by accessing the modem configuration panel either by rebooting the modem abruptly, by turning it off, or by removing the power plug. In another article, we have seen how to tell if the modem router is broken.

Carrier cable problems

If the modem is not the cause of the optical fiber slowdowns, the second suspect for the problems is carrier connection between the modem and the cabinet or the telephone exchange. On FTTC we will have the classic copper pair in the telephone socket, while with FTTH we will have the fiber optic cable that reaches the house. Problems with wires and cabinets are not at all easy to solve, but we can still give our contribution by following the suggestions below:

  • On FTTC line: we try to remove any sort of ADSL filter still present on the telephone socket and use a high quality RJ11 telephone cable.
  • Your FTTH line: if the fiber optic cable reaches the modem, we cannot do anything; however, if the fiber cable reaches the ONT (the wall terminal), we can try to use a shielded Ethernet cable between the ONT socket and the WAN port of the modem used.

If the problem persists, it’s worth it request assistance from the telephone operator.

Internet Protocol Problems

The third suspect for the fiber optic problems is the Internet protocol, that is the protocol that allows you to open web pages and access all services. Without going into specifics, just know that, in 90% of cases, the connection error is caused by server DNS, i.e. those servers used by all connections to convert web addresses into IP addresses (and vice versa). Failure to access DNS servers or their slow response can slow down (even dramatically) the fiber optic connection, until it stops completely (no web page opens anymore, with error DNS Probe Finished No Internet).

To solve it, simply choose a new DNS service from the modem or from individual devices, in order to obtain a much faster service than the DNS offered by the telephone operator. To learn more, we invite you to read the guides in the following bulleted list:

  • 5 faster and safer DNS addresses to protect your internet connection
  • Change DNS server in Windows 10 connection settings
  • How to set up DNS on the modem
  • How to change DNS on Smart TV
  • How to change DNS

If the problems involve other components of the Internet protocol (Gateway or public IP address), it is advisable to contact the operator’s assistance as seen in the previous chapter. If instead the problem is the private IP address of the network (an IP conflict between two devices for example), we can change IP on PC, Router and smartphone.

PC or browser problems

The last suspect for problems with slow fiber optics is the device in use at that precise moment (PC, smartphone, tablet) and its web browser. In this case we immediately try to connect to the modem with another device in our possession and check if the connection speed is sufficient, using a speed test service. If the connection speed on the other device is in line with the performance of our fiber optic line, we try to turn off and on the Wi-Fi connection or the whole device, so as to check if the error was only temporary.

If the connection problems with the device or browser persist, we recommend that you read the guides in the following bulleted list.

  • How to change default browser on Windows PC
  • If the PC is not connected to the internet, how to reset the network and web browsing
  • Troubleshoot Internet and network connection problems on the PC
  • Solutions to problems on the internet connection and wireless networks
  • Repair TCP and Winsock in Windows 10

If the problems concern Windows 10, let’s not underestimate the slowdowns due to malware (How to remove malware and viruses from infected computer) or faulty updates (reset Windows 10 (Reset PC).


By following to the letter all the indications of this guide we will be able to solve virtually all slow fiber optic problems, going step by step and trying all the common scenarios that a home user or small office user might encounter. In most cases the problem will be solved immediately; in the most serious cases, however, we will necessarily have to call for assistance.

Still on the subject of optical fiber, we can deepen the technological evolution by reading our guides on EVDSL, the alternative to optical fiber for fast Internet, e Gigabit fiber or 1000 Mega.


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