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[Bowdon]

I just thought I'd ask, as I am wondering are fibre lines immune to interference?

With Openreach announcing they are going to be extending their fibre network to poles and places closer to houses, I can imagine it wont be that far off that they will start to offer FTTP sort of packages as effectively they would only need to go from the pole to your house with fibre. So if this was the case would that eliminate all outside (as in outside your house) interference?

[kitz]

Generally speaking it certainly doesnt have the same issues as copper.  However multi-mode fibre optic cable which is mostly what BT use in the 'local loop' suffers from modal dispersion. 
OM4 (the aqua cable you see used by BT) is good for 1Gbps @ 1000m 

[JGO]

Fibre has been used in military service for it's immunity to interference, say in aircraft with space and weight limitations, since the 1970s. It isn't immune to EMP i.e. a nearby Atomic Bomb which darkens the fibre but all other forms of Electromagnetic Interference.

Kitz's point on wave interference dispersion is fair enough but who has that much useful information to send ? We have a family saying " You can find anything on the web, and some of it is actually true !"

[c6em]

What about in Cornwall where I would have thought it might be affected to some degree by ionization radiation from the radon gas from the granite rocks?

[JGO]

What about in Cornwall where I would have thought it might be affected to some degree by ionization radiation from the radon gas from the granite rocks?

Don't know but suspect any associated semiconductors would suffer first.

[Bowdon]

That sounds pretty good.

So its possible that if BT/Openreach deploy this fibre to the pole technology, or to nodes, and then offer a full fibre connection, we could jump up the fibre table compared to other countries, to have full fibre.

I hope that everything goes to plan. I think when we get to a point when full fibre is the 'norm', we'll be in a different era. A bit like when we went from dialup to adsl connections.

[kitz]

Kitz's point on wave interference dispersion is fair enough but who has that much useful information to send ?

That would be the GbE links used between the dslam and exchange.   

Whilst single mode fibre is also used in some local situations, but the vast majority of fibre in use locally by BT Openreach is OM3/OM4.    OM3 and OM4 can easily be identified because of their aqua coloured jackets.

Modal Dispersion is an issue with multi-mode fibre optic cable.. and it does get attenuated over distance.
As can be seen in the table here, theres a vast amount of difference of available bandwidth at various distances ie 100Gb @ 100m, yet only 1Gb @ 1000m :/

With FTTP whilst you may have a single 1BFT to the premise, youve still got to take into consideration the capacity of the node links, which will be shared. 


-----
PS should really clarify..
That as far as the EU is concerned then no it shouldnt be an issue, but it is something that BT have to factor when installing FTTP.

[Black Sheep]

That sounds pretty good.

So its possible that if BT/Openreach deploy this fibre to the pole technology, or to nodes, and then offer a full fibre connection, we could jump up the fibre table compared to other countries, to have full fibre.

I hope that everything goes to plan. I think when we get to a point when full fibre is the 'norm', we'll be in a different era. A bit like when we went from dialup to adsl connections.

They have been doing exactly that for the last couple of years It all depended on whether your own Exchange was ear-marked for the full 'FTTP' (Fibre To The Premises), or 'FTTC' (Fibre To The Cab) product ?? I couldn't give a percentage as to how many Exchanges are, or going to be, FTTP in comparison to FTTC ....... but I will bet it's 5% or under ??.
I feel for the people of Rochdale for example, as they were ear-marked for FTTP, but when it was found their Exchanges 3-phase electric supply was already running at 90+%, which put the estimated installation costs a lot higher as they would have had to upgrade the supply. Instead, they went for FTTC ..... that's business for you. 

Once the FTTC (and it's sister, BDUK) programmes have completely rolled out, then I would suspect 'FTTP (oD) - On Demand will be the next logical step. I've no idea at all on pricing for FTTP (oD) at the minute, but would hope it gets cheaper as time goes by    

[Chrysalis]

Kitz's point on wave interference dispersion is fair enough but who has that much useful information to send ?

That would be the GbE links used between the dslam and exchange.   

Whilst single mode fibre is also used in some local situations, but the vast majority of fibre in use locally by BT Openreach is OM3/OM4.    OM3 and OM4 can easily be identified because of their aqua coloured jackets.

Modal Dispersion is an issue with multi-mode fibre optic cable.. and it does get attenuated over distance.
As can be seen in the table here, theres a vast amount of difference of available bandwidth at various distances ie 100Gb @ 100m, yet only 1Gb @ 1000m :/

With FTTP whilst you may have a single 1BFT to the premise, youve still got to take into consideration the capacity of the node links, which will be shared. 


-----
PS should really clarify..
That as far as the EU is concerned then no it shouldnt be an issue, but it is something that BT have to factor when installing FTTP.

interesting but considering the loop length to my cabinet is about 4km, something doesnt add up, is it possible they used the single mode fibre for the long runs?

I will admit the cabling I seen them inserting int the ducts to the cabinet across the road from me looked like an aqua colour.  But maybe they only used that stuff between the cabinet and the distribution point?

[guest]

Been a long time since I worked on optical wavelengths but a repeater/optical amplifier is the usual way of doing these things. There will in most cases be power available somewhere along the way in urban areas & its not exactly rocket science.

[kitz]

considering the loop length to my cabinet is about 4km, something doesnt add up

It certainly wont be one single 4km run of OM4 if thats what you are thinking.  There will be various nodes along the way consisting of splitters/repeaters/manifolds.


Every area is different, and its entirely up to BT what they use.   Without doubt someone will have had to have sat down to plan and cost the various options available depending upon the number of cabs and their distance from the exchange and locality.

They may use single mode fibre to a node for some really long runs...  or they may use say OM4 to cab 1 and then use a splitters and/or fibre optic repeater to reach cab2 etc.   There will be nodes for both fttc & fttp.. and no 2 area's will be the same.

OM4 is much cheaper than single mode fibre.  Walter is probably best to answer this, but iirc B4RN use repeaters every so often along their routes.

[Chrysalis]

yeah I was wondering about repeaters and the like, thanks.

[c6em]

Yes Walter will certainly know - however I was under the impression B4RN were installing single mode fibre operating point to point from the village cabinet to each house. 
No idea about from the cabinet back to where ever it goes.....
I can also recall seeing somewhere them saying that in the future by changing the optics at each end it could in the future operate at 10 or even 100Gbps which again would suggest single mode.

[kitz]

You may well be right since B4RN is a completely different kettle of fish.  B4RN has a total of circa 700 customers over all towns/locations, whereas in theory just 3 BT cabs could hold the same amount of customers. 

Multimode fibre only really works out cheaper if you have a large amount of consumers branching off from one node who are within 'x' meters.   The layout of B4RN with lots of rural properties would need a very different design than urban towns & cities.  I know for example at my exchange, there are about 7 cabs each within about 200-300 m from each other which all radiate &  branch off in different directions and therefore ideal situation for OM4. 

This is precisely why I said earlier BT would have someone to plan and look at each individual town to see which is the best (and cheapest) way to route and which type of fibre cable to use.  I'm sure I can recall reading at some point though that B4RN did use repeaters though.  They will also likely use a different type of single mode fibre as their capacity requirements will be no-where near that of BTw's backhauls.

[kitz]

This is an example of BTw/OR single mode fibre..



According to documentation "BTw uses a combination of the following cables in their network : Remote Single Mode Fibre, Local Single Mode Fibre, Multi-mode Fibre 62.5 μm @ 850nm.  Aqua jacketed cable is usually OM3 or OM4 (50/125) which are capable of 1Gbps @ 550/1000 meters respectively."



Compared with this for b4rn, who may also use different types of fibre optic cable

According to
this they use Webro 192 Fibre Singlemode G657/A Mini Cable

[youtube]404As6-NrPM[/youtube]

yet this image here could imply from its jacket colour multi-mode fibre so Im a bit confused.   Note they had to replace that section of cable with a different type of cable so I dont know.