This topic

Full Fibre Installation

linkyyork — Thu, 29 Jan 2026 12:34:32 GMT

Had the installation last Monday, and it has gone from bad to worse. Speed has not been anywhere near the minimum speed. Trying to contact BT is going round in circles, but they have reset the modem with no effect. However, looking at the wall plate, there are four green lights, I assume that as the LH one is not lit, the next is flickering, and the other two are lit. Should the LH be lit?

Re: Full Fibre Installation

Kimberlin — Thu, 29 Jan 2026 12:42:09 GMT

@linkyyork

On my ONT, working from left to right: The first light on the left is flickering, the next one in, there is no light and the 3rd and 4th lights on the right, are permanently illuminated.

Re: Full Fibre Installation

iniltous — Thu, 29 Jan 2026 13:03:36 GMT

The only light on an ONT that is really important is the PON light , if this is lit and steady green then generally everything is OK , the others lights are power ( obviously no power , it’s not going to work ) and LAN ( generally flickering or on , this is activity between the ONT and router , so depends to an extent what the router is doing ) ….the only other light and it depends on the ONT manufacturer design is LOS , not every ONT has 4 lights , some have 3 as they have a combined PON/LOS , light , if there is a LOS light illuminated ( loss of signal ) , that’s red ( not green ) and if it’s lit there is clearly an issue with the input signal to the ONT , so from what you say nothing seems amiss, the unlit light is probably the LOS light , and that’s what you want , you don’t want a LOS light lit .

How are you measuring speed ? , if it’s with a wireless device it’s of no real use as WiFi performance has too many variables, is it just speed tests that have you ‘upset’ or are you experiencing real world issues ?

What profile speed are you purchasing, what is your minimum speed guarantee and what are you getting on a speed test ( even if it’s on a wireless device ) ?

Unless there has been a provision error , so for example you pay for 500Mb but they incorrectly set your ‘account’ as 150Mb then generally FTTP either works correctly or doesn’t work at all .

Re: Full Fibre Installation

linkyyork — Thu, 29 Jan 2026 13:10:06 GMT

Thanks. That could be the problem, but it's virtually impossible to contact a real person at BT. We started on Monday at around 55Mbps, but it's now down to about 10 Mbps.

Re: Full Fibre Installation

Kimberlin — Thu, 29 Jan 2026 13:13:55 GMT

@linkyyork

You didn't actually mention what speed you have signed up to? What FTTP package are you on?

Re: Full Fibre Installation

gg30340 — Thu, 29 Jan 2026 14:00:40 GMT

See link for the lights on the ONT.

What do the lights on the Openreach modem mean? | BT Help

Re: Full Fibre Installation

chrisjp — Thu, 29 Jan 2026 14:17:22 GMT

But there surely can't be a FTTP package offering just 10 Mbps...can there?

Re: Full Fibre Installation

WSH — Thu, 29 Jan 2026 14:53:30 GMT

Just to round out the picture of what the lights mean. The latest ONT, (the Adtran 611), does not have a LOS light. What it has is an Alarm light. The manual says this.

Power

Off Power is off

Green Power is on, self-test passed, normal operation

Green Flashing Unit is powering up

Optical (Seems to be what they call PON)

Green ONU ranged, authenticated, and configured with services

Green Flashing (Fast) ONU is ranging and synchronization process in progress

Green Flashing (Slow) ONU ranged and authenticated but not configured with services

Red PON is down due to LOF/LOS

LAN

Off No Ethernet connectivity

Green Ethernet connectivity present, no activity

Green Flashing Ethernet connectivity present, activity detected Interface operation state is up and packets Tx/Rx detected on the interface

Alarm/Update

Off No alarm detected

Green ONU software download complete and software upgrade in progress. ONU LED will turn off once upgrade is successful

Green Flashing ONU software download in progress

Red ONU is powered up and PON operational state is up and ONU software upgrade failed.

New ONU software not operational due to any of the following reasons:

■ Software image download failed

■ Software image flash write failed

■ Software image activation failed

■ Software image commit failed

Re: Full Fibre Installation

linkyyork — Thu, 29 Jan 2026 15:46:04 GMT

Sorry for the long pause while I rested my brain.

BT have been on to me and showed me their readings up to modem, and it was more or less full speed, so god knows what I will do now, as a speed test is only giving around 30Mbps, which is less than the old part copper broadband. The guaranteed speeds are 425 and 73.

The lights I mentioned earlier are OK according to BT, so I do not know where to go next.

Thanks for all the info, etc.

Re: Full Fibre Installation

licquorice — Thu, 29 Jan 2026 16:00:36 GMT

Perhapos if you answered whether you are testing via a device connected to WiFi or Ethernet we might be able to give some advice.

Re: Full Fibre Installation

pddco — Thu, 29 Jan 2026 17:25:13 GMT

In all these cases the best speed tester to use is within the MyBT App. It’s under the My Products section, Broadband. It tells you the speed to the hub and , on the same page, the speed to the device that requested the speed test.

So, you’ve got a problem with the service ( to the hub) you can see that instantly in plain sight. And if you’ve got a problem with your “customer side” stuff like WiFi or a dodgy Ethernet cable, you can see that too.

There are quite a few advocates saying using fast.com.. But why would you, if you’re a BT broadband customer? Or am I missing something?

Re: Full Fibre Installation

gg30340 — Thu, 29 Jan 2026 17:26:49 GMT

Fast.com is what the Openreach engineers use.

Re: Full Fibre Installation

licquorice — Thu, 29 Jan 2026 17:33:15 GMT

Not sure how the speed to the hub can be measured with the MyBT app with FTTP, the speed will always be 1Gbps from the ONT to the hub regardless of speed to the ONT.

Re: Full Fibre Installation

pddco — Thu, 29 Jan 2026 18:16:30 GMT

What??? It’s the speed from wherever the server is that instigates the test to the customer’s hub via the broadband service that’s been delivered. Surely.. I’ve got FTTP and yes the Ethernet link speed from the ONT to the Hub is indeed 1Gbps but that’s not what’s being checked is it? I run a test and I get 150Mbps download to the hub which is bang on for my fibre 100 service that I’m paying for..

And of course Openreach will likely use fast.com as they’re absolutely not bothered about the customer’s WiFi performance. They’ll simply use an Ethernet cable either from a Hub port or the ONT.

If you use fast.com from a WiFi device it’ll only tell you the speed from the fast.com server or whatever to the device. So will be the lesser of the broadband service speed being delivered by BT in this case and whatever the vagaries of the WiFI connection have on the speed between the hub and the device.
If the WiFi is great it’ll damn near match the broadband service speed. But if it turns out less than you’re expecting then what you definitely don’t know is wether that reduced speed is due to a service speed issue (to the hub) or between the hub and the device.. Think I’ve said that before.

Now , if you were to use a good quality (not dodgy) Ethernet cable connected to hub and then to a PC running fast.com then agreed that speed result should match your expected broadband service speed.

Re: Full Fibre Installation

licquorice — Thu, 29 Jan 2026 18:01:58 GMT

I have absolutely no idea what's being checked, but to me 'speed to the hub' means the Phy speed to the hub but clearly not.

Re: Full Fibre Installation

Jane2018 — Thu, 29 Jan 2026 18:50:31 GMT

I got FTTP recently (but via Community Fibre, not BT but have kept my BT broadband as back up for now). The speed quoted is very low indeed particularly if we are talking about an ethernet cable from there into a computer. I installed a new network adapter card by the way into my new computer so that my computer could get a higher speed (I have up to 5GB - very fast with CF and usually get between 3.4GB to 4.8GB on my computer with ethernet cable using the fast speed checker of which I had never heard until the installation man suggested it rather than my usual). Before I installed the new card thing into my PC my PC was capped at 1GB although 1GB is more than enough for most people anyway.

Re: Full Fibre Installation

Kimberlin — Thu, 29 Jan 2026 18:51:30 GMT

@gg30340

Thanks for that. Not heard of that speed test before. Just ran it ethernet connected into my laptop, 510mbps on a 500mbps package 👍

Re: Full Fibre Installation

linkyyork — Thu, 29 Jan 2026 22:08:08 GMT

Thank you for all the comments and queries. Can I just say that before Full Fibre, we were on FFTC, and on that, both of our computers were upstairs, with the modem connected to one computer with the yellow Ethernet cable. We never got to full speed, around 60, but it seemed OK we were quite happy to accept that figure.

When the engineer came to fit the FFTP he asked where the modem was and said it should come downstairs, where it is now fitted, connected to the wall socket with the Ethernet cable.

Now today when the BT man phoned he said they had tested the cable from the Exchange to the house and it was at 400+ . He asked if I had tested it on a mobile and as I hadn't he sent something that allowed me a carry out a speed check on the phone. When it was completed twoboxes came up. one which was the test for the phone, and the other one was the test to the house which showed the results of 400+ plus the up measurement of around 70. The BT man could see the results of the test his end

The speed has gone up a bit on my computer but only 50+

The wife has done a speed test downstairs and that came to 400. My mobile showed a lower speed.

Right where do I go from here, because I was surprised the fitter on Monday didn't check it was working OK going only by the light . Can I get BT to come in the house and offer some advice at how to proceed.

Thanks again to everyone.

Re: Full Fibre Installation

licquorice — Thu, 29 Jan 2026 22:22:52 GMT

I'm afraid the problem is yours, not BT's. Internal wiring and WiFi coverage are entirely your responsibility.

Increasing the speed to the house will not increase the speed of WiFi. With FTTC, the speed of the broadband would have been the limiting factor, it is now your WiFi.

You can either invest in a WiFI mesh system or powerline adapters with WiFi and Ethernet

https://community.bt.com/t5/BT-Devices/What-disc-do-I-have-BT-Complete-Wi-Fi-or-BT-Whole-Home-Mini/td-p/1970997 for BT options, but there are many tird party systems or

https://www.tp-link.com/uk/home-networking/powerline/ for powerline solutions

Re: Full Fibre Installation

WSH — Thu, 29 Jan 2026 22:21:20 GMT

Presumably by “modem” you mean the Smart Hub 2 router. (The modem is the box with lights that the engineer fitted to the wall – called an ONT or Optical Network Terminal).

You say the Smart Hub has been moved downstairs so you must now be connected via Wi-Fi. That will really knock the speed down. You really need ethernet cable to get the full benefit of the FTTP speed increase.

Edit: Oops, Licquorice beat me to it...again.