This topic

Flashing PON light

speedbirdchris — Tue, 12 Mar 2024 06:05:42 GMT

Good morning ,

I’ve been reading through the previous posts and wondered if anybody can help. I’ve just joined BT.

My FTTP was installed last Wednesday and an hour after Openreach left the connection dropped and was left with a Green flashing PON light. BT organised another Openreach installer for Friday, they arrived and it was because the serial number for the ONT wasn’t registered correctly to my property , this resolved the issue, however an hour later the same happened again. Engineer was booked for Monday as external works required but they failed to show.

I called BT again to chase the fault and tried speaking with the FTTP team but the call agent I had didn’t appear to be from the team, and took me through the normal restarting the hub . I asked her to check the serial number was correct for the ONT and she clearly didn’t know what I was talking about. Another engineer is now booked for Friday.

Is there anyone who can help ?
I’m lost without having internet ,

Thank You 🙂

Re: Flashing PON light

ptrduffy — Tue, 12 Mar 2024 08:20:45 GMT

Call the dedicated FTTP team on 0800 587 4787 - if you fall through to regular CS hang up and try again. Give them the ONT serial number and hopefully they can sort things out.

Re: Flashing PON light

speedbirdchris — Tue, 12 Mar 2024 09:20:51 GMT

Thank you so much , I will try to speak to them again 🙂

Re: Flashing PON light

iniltous — Tue, 12 Mar 2024 10:23:20 GMT

That’s a odd problem, if the original tech left the service working ( so PON light steady green ) then the ONT was successfully authenticated , so at that point the appropriate serial number was entered , otherwise you would never have had a steady green PON light and internet access , but then you somehow lost authentication hence the return to a flashing PON , another visit re authenticated the ( presumably original ) ONT but it didn’t last , unless you are the only worker on your particular splitter , then chances are any headend issues that were causing your ONT to drop out , potentially would cause all ONT’s ( not just yours ) on the same splitter ( so up-to 30 users ) to all ‘drop out’ , as optically they are all identical , which suggests to me your ONT may need replacing , unless the second visit actually replaced the ONT .

Re: Flashing PON light

speedbirdchris — Tue, 12 Mar 2024 11:31:24 GMT

Thanks for your detailed reply.

When the engineer returned the ONT wasn’t replaced he just called and had the serial number authenticated again with open reach.

My Neighbour is also connected to the same Head End and has no issues with their FTTP connection.

Openreach are visiting the property again on Friday so will see what they say / I will suggest they replace the ONT.

Many Thanks for your reply

Re: Flashing PON light

speedbirdchris — Fri, 15 Mar 2024 16:05:37 GMT

So I had a lovely Openreach engineer visit today , who unfortunately still hasn’t been able to connect me. He changed the ONT and re-spliced the fibre also checked the head end and just can’t get me connected. He has issues trying to speak to someone higher at Openreach .

I’m lost what to do now !

Re: Flashing PON light

iniltous — Fri, 15 Mar 2024 17:42:47 GMT

Without knowing what the tech did ( apart from a probably unnecessary re-splice and a worthwhile ONT change , to eliminate the ONT as the issue ) there isn’t a lot more to go on, presumably they will return with a PTO ( precision test officer ) or a senior tech to investigate further.

If your original ONT had never authenticated then suspicion would fall on the optical path , basically the optical signal / light from the headend ( indicated by the PON being lit and the LOS not being lit ) would not coming from the correct SASA ( splitter array sub assembly ) , because it did authenticate briefly, and then failed , then you would lead you to think the optical path is fine , unless someone has intervened in the optical network a few minutes after your tech has installed your original ONT and left an error , but that would affect all users on the same SASA as you …it’s pretty strange, unless you are the first and only user on your SASA .

Re: Flashing PON light

speedbirdchris — Fri, 15 Mar 2024 18:23:48 GMT

The Poor engineer was here for 4 hours ! He was totally unsupported by the openreach helpline who wouldn't allow him to escalate it further.

I have limited tech knowledge, but the light readings were perfect, and all the routing was fine as well. He went out into the street and swapped something with the neighbours to see if it would work. The neighbours internet worked fine, but wouldn't with mine.

Openreach have now booked another appointment on Monday, but I'm unsure what help that would do.

Re: Flashing PON light

iniltous — Sat, 16 Mar 2024 09:52:30 GMT

If the tech in effect went to the CBT and switched your connection with a neighbour, because each connection on the CBT is optically identical, if your connection didn’t work ( even though you were on ‘their’ CBT port ) and their connection continued to work even though they were on ‘your’ CBT connection, it’s going to be an odd ( unusual ) issue …possibly explaining the techs confusion.

The way GPON works is all downstream ‘data’ is broadcast by the OLT , and all ONT’s on the splitter receive that broadcast data simultaneously , each ONT ‘filters out’ the data addressed to itself , and ignores all the other data , the upload is different, each ONT uploads individually using ‘time slots ‘ so the headend knows which ONT is talking to it , if the data is corrupted within the headend for your particular upload ‘slot’ on the PON , then your ONT and the headend ( OLT ) cannot successfully ‘talk’ to each other , leaving you out of service , this could explain your somewhat weird symptoms, the optical path apparently fine , the ONT changed but still no service.

My suggestion ( if this hasn’t already occurred to the techs that visit ) is that your BT profile is ‘ceased’ , clearing out any potentially corrupted data from the system ( you won’t effectively exist on the OLT anymore) and then you are re provisioned as a brand new BT customer, with new data .

Obviously I can’t say with any real certainty this is the issue and my suggestion is the answer, but it’s certainly an avenue for them to explore…if that doesn’t fix the issue , it points to the actual headend electronics ( the OLT ) and that’s probably way above the visiting techs ‘ pay band’ , it may even need the OLT vendors engineers ( Nokia , Adtran ) to get involved

Re: Flashing PON light

speedbirdchris — Wed, 20 Mar 2024 00:43:17 GMT

Thanks for all the information and possible solutions . I finally managed to get the fault rectified by reaching out to Openreach directly who were amazing! They managed to rectify the issue. It appears that somehow they had got many ONT serial numbers listed for my property.

After removing them all and adding the correct one they rebuilt my profile with just the one correct ONT serial number and now is working as it should .

thanks for all your help and tips !

Re: Flashing PON light

Anonymous — Wed, 20 Mar 2024 07:40:42 GMT

Glad you're sorted but it may be useful for others if you could detail through which channel you were able to get Openreach involved.

Re: Flashing PON light

Seven1 — Mon, 11 Aug 2025 09:00:36 GMT

Hi, I’m pretty sure I’m having the same issue. How did you manage to reach out to openreach directly? They have no customer service for broadband installations AFAIK

Re: Flashing PON light

imjolly — Mon, 11 Aug 2025 09:14:05 GMT

if you are a BT broadband customer you need to phone CS 03301234150 and report fault have you check for problems in your area in case just not you with problems

Re: Flashing PON light

Seven1 — Mon, 11 Aug 2025 09:27:58 GMT

I’ve called EE/BT CS multiple times and have had no success. Been without working internet for over a month now. They can’t get anyone at Openreach to come and check the issue, just get told it’s been escalated every week. Very disappointing

Re: Flashing PON light

imjolly — Mon, 11 Aug 2025 09:43:49 GMT

are you a BT broadband customer?

have you checked for outages in your area?

Re: Flashing PON light

WSH — Mon, 11 Aug 2025 09:47:57 GMT

Start talking about your right to terminate and leave. That should get them moving, although ultimately, even BT are dependent of Openreach getting their finger out.