Recommend:
To the knowledge base
Knowledge document #55

The FRITZ!Box's Power LED flashes

The FRITZ!Box's Power LED flashes? ✔ Here you can find out what this means and how to solve the problem.

Although the FRITZ!Box is configured for use with a fibre optic connection, the FRITZ!Box does not establish a fibre optic connection. The Power/Fiber LED on the FRITZ!Box flashes continuously and the message 'Fibre optics interrupted' is displayed on the 'Overview' page of the FRITZ!Box user interface.

One of the following messages is displayed in the fibre optic information or in the event log of the FRITZ!Box:

  • 'The FRITZ!Box checked your connection and could not find a fibre optic connection.'
  • 'Fibre optic cable not connected [...]'
  • 'The fibre optic connection is interrupted.'

Simply proceed as described below. After each measure, check whether the problem is solved.

1 Making sure that the fibre optic connection is supported

  1. Check the documentation for your fibre optic connection or ask your internet service provider which standard was used for your fibre optic connection (AON, GPON, XGS-PON).
  2. The FRITZ!Box can be connected directly to an AON or a GPON fibre optic connection (ITU-T G.652 or ITU-T G.984).
    • The FRITZ!Box cannot be connected to an XGS-PON fibre optic connection (ITU-T G.9807.1). However, you can configure the FRITZ!Box for the internet connection via 'WAN' and use it behind the fibre optic modem from the internet service provider on this type of connection.

2 Setting the country of use

  1. Click on 'System' in the FRITZ!Box user interface.
  2. Click on 'Region and Language' in the 'System' menu.
  3. Click on the 'Region' tab.
  4. Select your country from the drop-down list. If your country is not displayed, select 'Other country'.

    Important:When the regional options are changed, the phone settings (for example telephony devices, call diversion settings, dialling rules) are reset and must be reconfigured.

  5. Click on 'Apply' to save the settings.

3 Checking the cabling

Errors in the cabling often go unnoticed. Therefore, make sure that the FRITZ!Box is correctly connected to your line:

  1. Remove all cable extensions and adapters between the FRITZ!Box and the fibre optic socket.
  2. Use an undamaged cable to connect the FRITZ!Box with the fibre optic socket. The fibre optic cable may not have any kinks or be damaged.

    Note:The FRITZ!Box has an LC/APC socket (compact connector, angle polished). Depending on the fibre optic socket, you may need to use a fibre optic cable with an adapter or a cable with different plugs on both ends. Normally the cable length in the home does not matter.

4 Testing a different cable

The cable that connects the FRITZ!Box to the fibre optic connection could be defective. Therefore, test a different cable:

  1. Use a different fibre optic cable (for example from a different fibre optic modem) to connect the FRITZ!Box to the fibre optic socket.
  2. If the Power/Fiber LED lights up constantly after 10 minutes, the fibre optic cable used before is defective and must be replaced.

    Note:Fibre optic cables can be purchased from electronics retailers. You can find information on the different types of plugs and polishing in the guide FRITZ!Box: Which fibre optic cable do I need?.

5 Installing the latest FRITZ!OS for the FRITZ!Box

Install the latest version of FRITZ!OS because it contains improvements for different fibre optic connections that can resolve the error:

  1. Manually update FRITZ!OS.

6 Contacting your provider

If the FRITZ!Box still does not establish the fibre optic connection, you may have to have your internet service provider unlock it, or the fibre optic connection may not have been activated yet, or it is disrupted:

  1. Contact the customer service of your internet service provider and have them unlock the FRITZ!Box for your fibre optic connection and check your fibre optic connection, if necessary.
    Modem ID on the FRITZ!Box's type label
    • Depending on the provider, you can either call their customer service or use an activation portal to activate it. With some providers, the FRITZ!Box's 'modem ID' given on the type label is required to unlock it.

    • ATTENTION!You may be charged for checking your fibre optic connection. Ask your provider about charges in advance!

Language selection