In reply to a post by Whitehall11:

I agree with Dect - PON Light from my limited experience terms an invalid / unable to establish a connection with the OLT. The Alarm Light sounds like a version of a LOS light, which suggests light is getting through, just potentially not enough!

Be good to see an actual photo of the ONT from the OP.

I suspect this isn’t either an ECI, Huawei or Nokia ONT!

Neither of these actually sport an “alarm”‘symbol LED - they have a separate PON and separate LOS labelled LEDs, which are very straightforward to distinguish if there is a no / insufficient light at to the unit (LOS is solid red) or a PON authentication/ misconfiguration issue (light is off or blinking rather than solid green).

If the OPs device has an “alarm” LED I suspect they may have an (hitherto very untypical for Openreach) an Adtran ONT.

The “alarm” symbol LED on an Adtran ONT actually doesn’t imply there is an optical issue (lack or no light) or a PON authentication issue. Rather it has to do with the ONT software operational state. Therefore even if there is no light this LED would be switched off.

In reply to a post by Pheasant:

The “alarm” symbol LED on an Adtran ONT actually doesn’t imply there is an optical issue (lack or no light) or a PON authentication issue. Rather it has to do with the ONT software operational state. Therefore even if there is no light this LED would be switched off.

This is good info that I wasn't aware of before stating my opinion about it being a configuration issue. In this case maybe the PON light being Red on this model is more significant due to there being no 'LOS' light on this model.

In reply to a post by TheBaron:

A serial number and barcode sticker
...
I can't find a matching picture on line.........

What are the first four characters of the serial number? You can ID the make of the ONT from the first fours chars.

S/N starts ADTN214 *****

That suggests an Adtran ONT ?, but its not the 401 or 411 I can find details of.

But I found it with image search

https://www.google.com/imgres?imgurl=https://helpfor...

https://www.google.com/imgres?imgurl=https://helpfor...

Yep it’s an Openreach version of an Adtran SDX 611 in white casing. They are ordinarily black in colour.

LED details here:

https://www.manualslib.com/manual/2238784/Adtran-Sdx...

Adtran SDX611 datasheet.

Here are some screenshots from the SDX 611Quick Start Guide, page 1, page 2, page 3 and page 4

You will see status lights sequence explained on page 3

I think we posted at the almost the same time 😂

The only difference to be aware of is the LED naming in the SDX Quick Start Guide is based on the standard Adtran symbols used. Its fairly obvious though...but "PON" on the Openreach version is the equivalent of "Optical" on the standard box

In reply to a post by TheBaron:

https://www.google.com/imgres?imgurl=https://helpfor...

Yes the standard black coloured SDX 611 is also used by HeyBroadband on their network.

See post with image from this hallowed forum 😃

[Note the LED sequence in "normal" operation - although there is no LAN cable plugged in, if there was that LED would be green too.]