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Author Topic: Couple of FTTP Questions - specifically Openreach FTTP  (Read 1615 times)

Black Sheep

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Re: Couple of FTTP Questions - specifically Openreach FTTP
« Reply #15 on: January 10, 2020, 05:32:38 PM »

Sorry my man. Optical budget = acceptable attenuation / loss of light between OLT and ONT. The more you split the light via prisms and the more splices and connectors there are in the cable run causing loss the shorter the total fibre run can be.

Forgot you are constrained by connectorised fibre lengths now!

Cheers for the explanation.  :)
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CarlT

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Re: Couple of FTTP Questions - specifically Openreach FTTP
« Reply #16 on: January 10, 2020, 05:58:27 PM »

Thanks in turn for all of your explanations. Sharing the knowledge is what places like this are for.
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Black Sheep

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Re: Couple of FTTP Questions - specifically Openreach FTTP
« Reply #17 on: January 10, 2020, 06:33:49 PM »

 :drink:
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aesmith

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Re: Couple of FTTP Questions - specifically Openreach FTTP
« Reply #18 on: January 15, 2020, 03:36:09 PM »

FTTP planning aims to get the max distance from splitter to CBT at 350mtrs. Then there is a max of 150mtrs from CBT to premises.
Ergo, 500mts in total.  :)

A couple more questions if people can bear it ..
(1) Black Sheep, just so I'm clear on terminology am I correct in thinking that the CBT runs multiple fibre back to a splitter?  And there can be more than one CBT off a single splitter?
I'm visualising the architecture as single fibre from exchange or wherever it's source, going to a single splitter, which in turn may go to several CBTs which in turn each may feed multiple properties.  Does that sound about right? 

Part of the reason for asking is that we're looking at a Community Fibre contract and there are some exceptions for excess construction charges even after the initial price is paid upfront.  Implying that individual householders who've shared the upfront cost might suddenly find their own connection is priced out of reach.  Some clarification is being sought but knowing the terminology will help.

(2) Second question.  I notice that BT gives guaranteed minimum speeds for their FTTP products.  How does that work, surely on fibre the speed should be known, or is this purely allowance for contention.  It's significant because if the speed was actually only 10 meg or even 25 meg then the end user would find themselves ineligible for the voucher scheme, as that requires a 30 meg speed.
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Black Sheep

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Re: Couple of FTTP Questions - specifically Openreach FTTP
« Reply #19 on: January 15, 2020, 06:56:45 PM »

A couple more questions if people can bear it ..
(1) Black Sheep, just so I'm clear on terminology am I correct in thinking that the CBT runs multiple fibre back to a splitter?  And there can be more than one CBT off a single splitter?
I'm visualising the architecture as single fibre from exchange or wherever it's source, going to a single splitter, which in turn may go to several CBTs which in turn each may feed multiple properties.  Does that sound about right? 

Part of the reason for asking is that we're looking at a Community Fibre contract and there are some exceptions for excess construction charges even after the initial price is paid upfront.  Implying that individual householders who've shared the upfront cost might suddenly find their own connection is priced out of reach.  Some clarification is being sought but knowing the terminology will help.



Absolutely right, pal .... the current build method is to utilise ULW36 (Ultra-lightweight, carrying 36 fibres,

The architecture could work two ways, from the splitter (This splits the light into 32 beams, from a single fibre fed which is from the head-end in the Exchange), the ULW could then feed directly to a CBT, or it could go through IJ's (Intermittent joints) before it reaches the CBT ... it's all dependant on distances when in the planning/surveying stages.

With 'Fibre cities' we work to a PON having a maximum of 120THP (Total Homes Passed) made up of four splitters - ergo - 30 premises per splitter. *There are exceptions to the 30THP per splitter, but it's as rare as hen's teeth.

Alas, 'Community Partnerships' and joint funding etc etc, is not my forte by any stretch of the imagination, I have no idea how that side of it works ?? Sorry.

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CarlT

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Re: Couple of FTTP Questions - specifically Openreach FTTP
« Reply #20 on: January 18, 2020, 09:52:55 PM »

(2) Second question.  I notice that BT gives guaranteed minimum speeds for their FTTP products.  How does that work, surely on fibre the speed should be known, or is this purely allowance for contention.  It's significant because if the speed was actually only 10 meg or even 25 meg then the end user would find themselves ineligible for the voucher scheme, as that requires a 30 meg speed.

Committed information rates on the Openreach FTTP products. Worst case performance under contention on the Openreach section of the network.

https://www.btplc.com/SINet/SINs/pdf/506v1p6.pdf
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aesmith

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Re: Couple of FTTP Questions - specifically Openreach FTTP
« Reply #21 on: January 19, 2020, 06:37:06 PM »

Thanks for the SIN.
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