ErrorBase
Independent technical referenceOfficial site
  • Networks
  • Fibre routers

ALARMA-ROJO-INTERMITENTE

Digi ALARMA-ROJO-INTERMITENTE on ZTE F8648P fibre router: not enough optical power

Verified with sources1 sourceReviewed Oct 3, 2026
Technician coming? See the 2 steps they must show you
Fibre Wi-Fi router with antennas
Solijon SolayevCC BY-SA 4.0Image source

Risk level

Low

Usually safe to check without specialist tools.

Urgency

Medium

Quick answer

If the Alarm indicator on your Digi ZTE ZXHN F8648P blinks red, the fibre interface is not connected or is not receiving enough optical power. Look at the fibre cable without touching it and restart the router without erasing its settings.

Safety first

Stop and check this first

  • Do not unplug, clean or bend the fibre cable or its connectors: checking them is the Digi technician's job.
  • Do not hold Reset for 5 seconds: according to the manual that restores factory settings. One second is enough to restart.

Safe checks you can perform

  • Identify the right indicator
  • Visual check of the fibre cable
  • Restart without losing settings
  • Report to Digi

Leave these tasks to a qualified professional

  • Do not attempt this professional task: Measure optical power
  • Do not attempt this professional task: Check patch cable and socket before replacing the router

What a technician must be able to justify

Technician visit

These are the steps they must carry out and show you. Tick them as they work: if steps are skipped, do not accept a part swap.

These are not instructions for opening or handling the equipment yourself. They are the checks that should support a technical conclusion.

  1. Measure optical power

    What they doThe Digi technician measures the signal at the wall socket and the router with an optical power meter.

    They must show youthe reading at the socket and the router against Digi's threshold.

    In writingthe section with losses and what was repaired.

  2. Check patch cable and socket before replacing the router

    What they doThe technician checks the patch cable, wall socket and optical connectors and only replaces the router if the reading points to it.

    They must show youthe reading before and after.

    In writingthe part replaced and why.

Before accepting a part or repair

Nothing has been shown yet. Do not accept a part swap based on the code alone.

Follow these steps

Note: Follow the documented order. An error code identifies the affected system, but it does not prove by itself which part has failed.

  1. Identify the right indicator

    No special tools

    Who:
    you.
    How:
    On the F8648P front panel find the Alarm indicator, separate from Fibre and Internet. Check it is Alarm that blinks red.
    Result that matters:
    Which indicator is red and how (solid or blinking).
    If Alarm blinks red:
    this page applies.
    If Alarm is solid red:
    it is a different state (emergency stop) with its own page.
    Evidence to keep:
    A photo of the front panel indicators.

    Evidence: Manual de usuario ZTE ZXHN F8648P XGS-PON ONT (DIGI Spain)

  2. Visual check of the fibre cable

    No special tools

    Who:
    you, looking only.
    How:
    Follow the fibre cable from the wall socket to the router's FIBRA port and check it reaches both ends and has no tight bends or crushing. Do not unplug it or clean the connectors.
    Result that matters:
    Whether something looks loose or damaged.
    If so:
    tell Digi so their technician checks it.
    If all looks fine:
    restart the router.
    Evidence to keep:
    Photos of the cable and the wall socket.

    Evidence: Manual de usuario ZTE ZXHN F8648P XGS-PON ONT (DIGI Spain)

  3. Restart without losing settings

    No special tools

    Who:
    you.
    How:
    With a fine pin, press the Reset button for one second with the router on. The manual says this restarts it without losing your settings.
    Result that matters:
    The Alarm indicator after startup.
    If Alarm goes off and Fibre stays solid green:
    the connection recovered.
    If it blinks red again:
    power still does not arrive; contact Digi.
    Evidence to keep:
    Time of the restart and indicator states.

    Evidence: Manual de usuario ZTE ZXHN F8648P XGS-PON ONT (DIGI Spain)

  4. Report to Digi

    No special tools

    Who:
    you, through Digi customer service.
    How:
    Give the model (ZTE ZXHN F8648P), that Alarm blinks red, that the cable looks fine and that you already restarted.
    Result that matters:
    That Digi checks the line and sends a technician if needed.
    If there is a network or cabling fault:
    the repair is Digi's.
    If they ask for more detail:
    share photos and times.
    Evidence to keep:
    Ticket number and date.

    Evidence: Manual de usuario ZTE ZXHN F8648P XGS-PON ONT (DIGI Spain)

Still not solved

If the error persists, stop here. See what the technician must do and show you.

Where this code applies

A code is meaningful only inside the right product and version context.

Primary scope

System
Networks
Brand
Digi
Product type
Fibre routers

Known code variants

  • digi fibra 10gb luz roja
  • digi router alarma roja parpadea
  • digi zte alarm red blinking
  • livebox 6s luz roja
  • livebox 6s zte alarma roja
  • luz alarma roja intermitente digi
  • masmovil alarma roja parpadea
  • masmovil fibra luz roja
  • masmovil router luz roja
  • router digi luz roja parpadeando
  • router masmovil luz roja intermitente
  • zte f8648p alarma rojo

What it means

The ZTE ZXHN F8648P manual published by Digi defines the Alarm indicator blinking red as the PON interface having no optical fibre connected or not receiving enough optical power. It is the fault family that measures the light arriving over the fibre: a cable unplugged, damaged or losing signal somewhere, or a network problem. The light does not say where the signal is lost and does not prove the router is faulty.

Warnings and stop conditions

  • Mediumeditorial warning

    Do not unplug, clean or bend the fibre cable or its connectors: checking them is the Digi technician's job.

    Evidence: Manual de usuario ZTE ZXHN F8648P XGS-PON ONT (DIGI Spain)

  • Mediumsource verified

    Do not hold Reset for 5 seconds: according to the manual that restores factory settings. One second is enough to restart.

    Evidence: Manual de usuario ZTE ZXHN F8648P XGS-PON ONT (DIGI Spain)

Symptoms and causes

Probable causes · in order

  • Fibre unplugged at the router or the wall socketPossible

    The manual gives this as the first reading of the state. It is visible if the green connector is out of place.

    Evidence: Manual de usuario ZTE ZXHN F8648P XGS-PON ONT (DIGI Spain)

  • Too little optical power from a damaged sectionPossible

    The cable is connected but not enough light arrives; the technician's power reading confirms it.

    Evidence: Manual de usuario ZTE ZXHN F8648P XGS-PON ONT (DIGI Spain)

  • Problem on Digi's networkPossible

    If the cable looks fine and the restart changes nothing, the loss is outside your home.

    Evidence: Manual de usuario ZTE ZXHN F8648P XGS-PON ONT (DIGI Spain)

Virtual technician

Does ALARMA-ROJO-INTERMITENTE still appear after these checks?

Answer a few questions to narrow down the likely cause and the safest next action. Guidance only - it never replaces a professional.

Start diagnosis

Sources and technical references

  1. 1

    Manual de usuario ZTE ZXHN F8648P XGS-PON ONT (DIGI Spain)

    DIGI Spain Telecom · 2021 · manual

Sources: Manual de usuario ZTE ZXHN F8648P XGS-PON ONT (DIGI Spain)reviewed 2026-10-03 · verified

Was this entry useful?