Print

Please login or register.
1 Hour 1 Day 1 Week 1 Month Forever
Login with username, password and session length

[Alex Atkin UK]

Not sure if this is the right section, but I was having a conversation with a Kelly engineer a few days ago that raised some red flags.

I was asking him what he thought of me trying to get a little more fibre into my home so I can move the ONT out of the way of a table.

I mentioned there is some slack outside and he said why not just pull it through, to which I explained those caps on the inside do not let you do that and I was wondering how you remove them without breaking them to pull more in.  He offered no suggestion.

I then talked about potential extension fibres inside, but that I didn't want to use one as you shouldn't be unplugging or adapting the fibre, the related risks to getting dust on it and if you accidentally pointed it into your eyes.  His response kinda alarmed me as he said "its not like its a laser, I've looked at it loads of times and not seen anything".

So not only did he completely not understand it IS a laser, he didn't seem aware its using wavelengths invisible to the human eye.  He seemed to assume there is a shutter on the plug that blocks it, AFAIK that is not the case, the invisible laser light just spills right out - you just can't see it.

This engineer was in the process of installing a fibre service at the time so he should know better!

[XGS_Is_On]

He's quite wrong in theory but okay in practice. By the time it reaches the home the PON laser has been split so many times the power level is pretty low so probably harmless. Not something to test repeatedly but that's how it is. His idea of a laser is a laser pointer: he's an installer not an optical engineer.

On unplugging or adapting the fibre it's fine. Every internal fibre connection in my home uses Invisilight with SC connectors so requires adaptors to convert to LC connectors to actually work with anything. The Openreach GPON has a flange and cable to adapt it from APC to UPC SC connector to feed my Huawei ONT, the YouFibre XGSPON has a flange and patch cable on it: didn't want the drop cable going into my cabinet.

I have this and this at home, apparently purchased on April 11th 2020, and clean both male and female sides of connectors every time I disconnect and repatch one.

He's actually kinda right about the shutter on the plug, too. ONTs don't start transmitting until they receive something, lasers on point to point fibre links negotiate transmit and receive power, they don't fire full bore straight away else they risk overloading the receiver on the other side, they are very careful until they receive something from the other side. Optical links negotiate power and, if they're so configured, speed. 1/10 Gbit negotiating optics are a thing.

From his point of view he's his eyesight and a bunch of successful installs. He doesn't need to know the details, just get things installed. He's likely gotten complacent about the laser light he's working with because he's been fine so often, and is fine with fibre connection as it's what he does day in, day out. I'm not convinced he'd have appreciated the conversation if it went down as you're describing and doubt it he'd have taken it on board beyond being polite in return.

[burakkucat]

<snip>

I have this and this at home, apparently purchased on April 11th 2020, and clean both male and female sides of connectors every time I disconnect and repatch one.

<snip>

Snap and snap! 

(I think I paid about £8 for each one . . . but it was a while ago.)

[Starman]

Regarding the fibre cleaning tools - what are they internally? Does it just wipe/polish the end or is there a fluid e.g. isopropyl alcohol fluid inside that perhaps evaprates away?

[XGS_Is_On]

Yeah there's a little well of alcohol in them and when you push to click it releases a bit of alcohol to soak the tip and wipes.

Seem to do the trick.

[XGS_Is_On]

I suppose my point is that folks that haven't played much seem to treat fibre with kid gloves. I've never seen a fibre engineer care about that the fibre they're splicing is connected to the CBT. When mine was respliced no-one touched the CBT.

The connectors are built specified with a number of connections and reconnections in the hundreds. As long as everything is cleaned all is well. The loss from a flange and adaptor is tiny compared to the 18 dB from a 1:32 split, the 24 dB from 1:128 split.

Just don't bend it too tightly, much as you shouldn't a copper cable, respect the minimum bend radius in the cable specifications, clean the male and female connectors every time you expose them and you're good to go. I've actually used connecting APC to UPC without an adaptor in lieu of an attenuator. Don't do that but goes to show it's not as touchy as you might think.

[Alex Atkin UK]

Yeah but its one thing to play rough and ready with your own kit, another if you somehow manage to cause degradation of the PON.  Its unlikely, but wouldn't Openreach fine you if they found you had modified something causing a network-wide issue?

I literally just want to take a little of the slack from outside as I need it inside, plus its hanging really low asking for rodents to nibble on it or the council garden service to chop it in two when cutting the grass.

Is there a trick to prising off those plastic retention caps Openreach put inside the house?  That's all I was trying to find out lol.

[licquorice]

They will only be Class1 lasers in any case. Its not until you get into the realms of the long haul core network with Class 3B and Raman lasers that any danger exists.

[burakkucat]

Is there a trick to prising off those plastic retention caps Openreach put inside the house?

I believe they are just clip-on. So just make use of the tools you would use when encouraging the separation of the back from the body of a service-provider's plastic CPE.

[Alex Atkin UK]

They will only be Class1 lasers in any case. Its not until you get into the realms of the long haul core network with Class 3B and Raman lasers that any danger exists.

For the customer I guess that is true, for an installer its probably ill advised to expose yourself too often as damage like that is likely cumulative.

I used to fry electronics for fun as a teen and I'm absolutely sure its why my Asthma got much worse in later life.  I also used to burn things with a magnifying glass which I'm sure hasn't helped my eyesight (though probably more risky than a Class 1 laser tbh).

[XGS_Is_On]

Yeah but its one thing to play rough and ready with your own kit, another if you somehow manage to cause degradation of the PON.  Its unlikely, but wouldn't Openreach fine you if they found you had modified something causing a network-wide issue?

You can't cause degradation of the PON with a bit of cable, a coupler and a flange. The ONT going bad and transmitting outside of timeslot is about the only thing that could impact the PON that isn't intentional sabotage. Sabotage is easy - get a high power 1550nm transmitter and either blind the OLT port to ONTs transmitting or cause it to shut down entirely.

[Alex Atkin UK]

I was under the impression fibre damage can cause reflections back along the fibre?

[XGS_Is_On]

Yes, absolutely, however the signal it's reflecting is so weak you're insanely unlikely to reflect enough of it back go cause issues.

https://www.thefoa.org/tech/ref/testing/test/reflectance.html for worst case across PON. - 20 dB added onto the -15 dB loss from OLT launch power due to split puts you a long way under the OLT launch power pre-split you have to compete with to break things.

The OLT is firing out at maybe 3 dBm, gets to you with split, insertion, splicing loss, etc, at -14 dBm and you are returning it at -34 dBm. By the time your reflection is back at the OLT side of your splitter you're at  -35 dBm, competing with a signal that's low modulation order and positive dBm.

To break anything realistically requires something generating signals in the upstream band.

[Alex Atkin UK]

Good to know.

[XGS_Is_On]

Yeah GPON and XGSPON are very robust. It's pretty hard to break either of them beyond a total cable break. They don't use high order modulation, they're BPSK / on or off, so are very solid.

The backbone links now actually emulate old school analogue - they are running 2 separate optical signals on a single wavelength modulated based on power and phase then combined to produce 256QAM signals - 8 bits per symbol instead of the 1 that BPSK provides.

These links are also nothing to do with what we have connected to our homes. Do not worry too much: you can easily break your own service but can't hurt the service of other folks on your PON