Fibre cab base layed, what are the tubes for?

Fibre cab base has been layed, but it has 1 big grey tube coming up inside it, and 3 small black tubes. What are these all for?

Power, fibre in, copper in, copper out I'd presume.

The big grey tube is the outlet for dropped packets.

Facebook post & pics

Edited by 8skellerns (Fri 22-Jan-16 22:36:48)

1.5 miles from the cabinet isn't good news for FTTC I'm afraid.

I know lol! Rediculous really as the exchange is 1.5 miles further up the road in the direction that I took the pic! You would think chopping my line in half would give me some speed boost!

So one bug grey tube and 3 small black tubes coming up in the base. What goes in the black ones and what goes in the big grey one?

In reply to a post by 8skellerns:

So one bug grey tube and 3 small black tubes coming up in the base. What goes in the black ones and what goes in the big grey one?

As I posted above.

I suspect the big tube will be for the power cable. And the other three for the copper and fibre cables.

Edited by deleted (Sat 23-Jan-16 16:02:16)

Given that the actual fibre line is blown through basically a small diameter black tube, I suggest that the latter's entry and possible exit to the next FTTC cover two of the small, black tubes, with the Mains Electricity Supply taking up the third small tube.

Also the fibre and mains are mainly employed at one end of "my" Huawei FTTC, it seems likely that they would be grouped together, at the DSLAM/Mains/Back-up Batteries end of the FTTC, generally apparently the left-hand side as viewed in the open doors.

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The "bent-over" small tube with an apparently yellow stripe seems likely to be the end of a fibre conduit/duct, coming in to the FTCC, waiting for the actual fibre to be blown through it.

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The much larger grey tube is probably for the multiple copper links to and from the associated, traditional PCP, from which the existing D-Side lines to the houses etc spread out.

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In the case of "my" FTTC, it can handle up to 288 Subscriber Connections, with two wires IN and two wires OUT

That is, 4 Wires times 288 Subscriber Connections, thus requiring 1152 wires, to pass between the FTTC and the PCP.

These are terminated on the back-plane with 288 sockets, in to which Filter Links are progressively plugged in batches.

In "my" FTTC when first activated, only the first 48 sockets had those Links plugged in, March 2014.

Another 48 were added in June 2015, as I spoke with the technician doing the work, taking about 5 minutes. He had about 20 FTTCs to do that day, so it appears to be the normal progression. I am not aware of any more being added since then.

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Taking the typical size/diameter of phone wires, the grey tube appears to be the only one capable of accomodating such quantities of wires.

AIUI FTTC cabinets are not daisy-chained wrt the fibre run. The fibre is split out at the aggregation point I think, which is usually nearby.

Afternoon RobertoS

The nearest location may be the three-section Under-Ground Chamber, about 5 metres away away from the FTTC.

Certainly, the Fibre ducting etc passes through that chamber and also the Link Cable to the PCP.

At present, I have not found the photos taken during installation.

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From memory, I think that cable was about 4 inches overall diameter (10 centimetres), with blue outer insulation.

Hence my suggesting that the larger-diameter, grey ducting is for the OP's FTTC to PCP Link Cable.

In my case, it appears in the UG chamber, heading "south" at the "north-west" corner nearest to the FTTC, then loops through about 180 degrees within the bulk of the chamber to head "north" out of the short "north" wall of the chamber to the PCP about 45 meters away, passing the FTTC on its travels, the PCP having a similar UG chamber close to it; but I have not been privy to its actual contents.

("Simplified" Compass" directions!)

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I often wonder if those advocating FTTP and FTTH realise the amount of work needed to provide ducting and fibre directly to any existing premises, houses etc.

In reply to a post by eckiedoo:

I often wonder if those advocating FTTP and FTTH realise the amount of work needed to provide ducting and fibre directly to any existing premises, houses etc.

Well every time I try and wearily explain that this is why FTTP masters Gigalcear only provide their network to a termination point at the property front boundary. From there though the front garden/drive and into the house is at the cost of the householder.
They know it's a whole load of aggro and they rather someone else pays for it - and deals with the 'difficult' property owners
So GC save on both money and time (lots of it).

Even BT's own FTTP trials as I recall mentioned how long that final "drop" took to do.

To be honest though I've almost given up explaining this for the umpteenth time to those who keep on about how, now that fibre is just down the street/at the G.fast node it would be so easy to do FTTP for all.

More pics

More pics further down facebook post

Another example here:
http://fibre.everestpark.org.uk/news/page/2/
It shows two of the larger cabinets being installed, and the ducting involved.

1. The larger grey ducts are for the copper tie cables to the PCP. Larger cabinets have a second grey duct. One photo on that site shows the grey duct on the right, and another photo shows tie pairs being installed on the right.

2. Other photos show ducting being placed for a run to the power cable, with a blue draw rope at one end, and emerging from one of the small ducts.

3. The larger cab has an extra small duct alongside the grey ones. It looks to me like it, and one of the other 3 small ducts, actually carry earth wires, complete with a connector ready to be bolted to the cab. We know earthing is an important consideration to BT, which no one has mentioned yet.

I guess the smaller cabs only need one earth connection.

4. That leaves one small duct for the fibre.

As I understand the way that FTTC cabinets are wired, the fibres themselves are point-to-point, running back to a nearby aggregation node where they are spliced to the spine. What enters the cabinet is a BFT - blown fibre tube - down which a 4-fibre BFU - blown fibre unit - is blown from an aggregation node.

There is no facility for fibre to be blown back out of the cabinet.

However, the BFT from the AN isn't always alone. It can be deployed as a cable with 7 BFT tubes leaving the AN, and arrives in an underground chamber near the FTTC cabinet. One BFT can be pulled out in a "tube intercept joint", to run alone into the FTTC cab. The other 6 BFT tubes in the cable can continue onwards, taking other BFU's to other cabinets.

So daisy-chaining can kinda happen, but down in the chambers, not up in the cab. And it is only tubes that chain, not the fibre itself.

On a recent news article, @ValueForMoney reckoned that BDUK had so far funded 17,500 cabinets, with 2,500-3,000 aggregation nodes - implying there may be around 6 cabs per AN. There's likely to be a fair few TIJ's involved in that, with some daisy-chaining. I have no idea whether those numbers are realistic.

TIJ:
http://www.prysmiangroup.com/en/business_markets/mar...

FTTC architecture, page 14:
http://www.bcs.org/upload/pdf/sfisher-090311.pdf

Huawei 288 Base

And again with rope pull for the power cable

Re the smaller black ducts with earth wires, it can be seen that one of these has an earth rod protruding from it; I assume the same is true of both ducts at either end of the cabinet, ie/ they fit two earth spikes.

The only ducting running away from the two cabinets I watched being installed are the two grey ducts, and the single black power duct. One of the black ducts therefore seems to be spare. It also means the fibre must go through the same grey ducting to the pavement chamber as the copper tie cables.

Edited by deleted (Mon 25-Jan-16 00:22:21)

Thanks WWWombat

See below, my reply to Olicuk

Thanks Olicuk, particularly for that second photo.

Using that photo and by measuring the width of "my" Huaweai 288 FTTC, it appears that the Internal Diameter of the Grey Tubes at the right, is about 3.25 inches (about 82.5 millimetres).

Thus the Blue Link Cable in "my" Underground Chamber must be slightly less than this, say 3 inches or 75 mm, at MAXIMUM; compared to my earlier guestimate of 4 inches.

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When the BT/OR technician was about to connect up the FTTC end of that Link Cable, he said that it was "100 link pairs", on a wild, dark, February 2014 day - would not like to attempt it myself, even in good weather!

Can any of you comment on the accuracy of my recollections and more recent measurements; and whether a single "100 link pairs" cable would provide sufficient wire pairs for the full capacity of 288 VDSL connections of a Huawei 288 FTTC Cabinet?

Definitely a 288 FTTC Cabinet.

Edited by deleted (Mon 25-Jan-16 11:04:39)

You'd need 6 x 100 pair cables to make full use if a huawei 288 cab.

In reply to a post by olicuk:

The only ducting running away from the two cabinets I watched being installed are the two grey ducts, and the single black power duct. One of the black ducts therefore seems to be spare. It also means the fibre must go through the same grey ducting to the pavement chamber as the copper tie cables.

Perhaps the "spare" duct allows for future expansion, with a second cabinet or (current thinking) a power pillar for G.Fast. It'd make sense for BT to want to feed power into such boxes in an easier fashion than has happened for the first box on site.

It is certainly possible that the fibre tube cable is also routed through the grey ducts. In fact, looking at some of these photos, the fibre termination space appears to be over on the same side as the copper termination:
http://www.kitz.co.uk/adsl/fttc-cabinets.htm

Thanks Ribble.

What diameter are the individual Link Cables, over their outer-insulation?

I assume that would be three Link Cables per Grey Duct?

Would one duct be used for the diverted, lengthened E-side; and the other for the D-side; or as there is apparently only one Link Cable locally, are the E-sides and D-sides, routed through as a mix in the one Link Cable?

My thanks again.

Edited by deleted (Mon 25-Jan-16 12:00:47)

90mm duct seems to be common for Openreach, for copper cables - they specify it a lot within the Developer's Guides. They use 50mm duct for the final drop into homes.

I'm not sure about that "blue link cable" though.

Some examples of D-side cables can be found on this page:
http://www.btcables.com/products/voice/outside-plant...

That tells us 100-pair cable, unarmoured, meeting CW1128 is 22mm diameter, while 100-pair cable meeting CW1326 is 25mm diameter. "Thumb-sized", unless you have dainty fingers. Even armoured cables aren't much fatter - and I doubt they need to use that within the ducts.

I don't think you'll find anything bigger than 100-pair cables involved in the tie-pairs. Or, indeed, in much of the D-side at all.

The Everest Park site has another example photo:
http://fibre.everestpark.org.uk/wp-content/uploads/2...

I wonder what you saw?

In reply to a post by eckiedoo:

Would one duct be used for the diverted, lengthened E-side; and the other for the D-side; or as there is apparently only one Link Cable locally, are the E-sides and D-sides, routed through as a mix in the one Link Cable?

I'm pretty sure you won't find a case where one cable houses pairs used to carry both the E-side tie and the D-side tie.

That kind of wiring has the potential to cause crosstalk issues if it were allowed to occur randomly in the network, so wouldn't be considered best practice.

The way we use tie pairs in FTTC wouldn't actually cause crosstalk issues right now, because ADSL signals are never sent through these wires, and VDSL signals only in one half, in one direction. Edit: It might cause issues on the voice circuits though.

But you never know how the network will evolve in future. So sticking to decent wiring practice makes sense.

However, I think it is fine for the E-sides and D-sides, once kept in separate cables, to have the cables routed through the same duct.

In fact, it must be happening for the cabinet of the OP. They only have one grey duct.

Edited by deleted (Mon 25-Jan-16 12:36:16)

My thanks again, WWWombat.

In the meantime, I had been working out the maximum diameter for three, circular cross-section cables in a 3 inch duct, as being about 1.4 inches (about 35 mm), without distortion or squeezing.

So your "25 mm" makes sense for ease of insertion, drawing through etc.

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Mentally, I had been thinking that the Link Cables would be a minimum of 10 Metres installed length; but seeing the apparent "excess" of the three hanging over that FTTC door, it suggests quite a bit more is used!

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Also my thanks for that link.

It was interesting to read the detail in the last two tables covering American Standards, particularly the right-most column covering attenuation.

Those Column headings of :-

Attenuation @ 0.772 MHz
(dB/305m)

are intriguing!

Why "0.772 MHz" and why "305" Metres?

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I have been searching PCs and Cameras for my photos of the U-G Chamber, to no avail so far.

That I recollect, most of the other cable, ducts etc were black; and none doubled back in any sense.

Only the blue one.

Had troubles with my main PC about that time.

If another opportunity turns up, I'll be out there with camera, the U-G Chamber is about 5 M from our lounge window; but as you and others will be aware, very rarely opened.

Hopefully, the FTTC may be opened at the same time, so that I might get photos down at the floor entry level.

Incidentally, most of the work was done by KELLY, as elsewhere in town, with the more skilled aspects being done by BT/OR.

Although stretched out from the November 2013 start of "cutting turf" to March 2014 RFS, it was neat and tidy etc; and when on site, there was no obvious waste of time.

The early upgrades at the PCP were mainly done by Kelly; but over the past six months, it appears to be BT/OR.

And those generally have been slowing down recently, tending to confirm BT's figure of about 30%.

In reply to a post by eckiedoo:

In the meantime, I had been working out the maximum diameter for three, circular cross-section cables in a 3 inch duct, as being about 1.4 inches (about 35 mm), without distortion or squeezing.

So your "25 mm" makes sense for ease of insertion, drawing through etc.

There is a 2010 study by Analysys Mason on "poles and ducts" for Ofcom, where they looked at a sample of poles, ducts and chambers, to help inform Ofcom about the costs of PIA.

I just took a quick look again ... and the document confirms 90mm duct.

One task they undertook was to estimate how much spare duct space there was between chambers. For 90mm duct, they specifically measured it in terms of how many "tubes" of 25mm could fit through (partly because the pulling rod is 25mm, and partly because it also happens to be a common sub-duct size). They reckoned a "full" 90mm duct carried 7 of these "tubes" of 25mm.

It was interesting to read the detail in the last two tables covering American Standards, particularly the right-most column covering attenuation.

Those Column headings of :-

Attenuation @ 0.772 MHz
(dB/305m)

are intriguing!

Why "0.772 MHz" and why "305" Metres?

As it is ANSI, I suspect they prefer to measure in feet. 305m = 100 feet?

I don't know why they use 0.772MHz, but it seems to appear in a lot of specifications - both in voice cable, and in data cable such as cat 5.

Why "0.772 MHz" and why "305" Metres?

As it is ANSI, I suspect they prefer to measure in feet. 305m = 100 feet?

1,000 feet

What cab would be placed on the base pictured on my facebook link?

Small Huawei 96 port cab

Just been to the pcp and found the cab placed onto the base! Its not bolted down though, it rocks and sounds hollow!

May need to add a 2nd earth rod if the 1st does not provide a sufficient earth reading

In reply to a post by ggremlin:

1,000 feet

Doh!

Does the large Huawei cab have more stringent earthing requirements?

I can understand an extra earth rod being cast into the base, just in case. But I'd expect it to be allowed for while casting the base, and appear in the smaller bases too.

In which case may just be a shell to cover and protect base, as cabs are delivered in a big plywood box with all the electronics pre-installed.

Thanks again, WWWombat.

I followed that through, by checking that seven 25 mm circles would fit "comfortably" in the 90 mm diameter.

One central cable, with the other six distributed in the annular gap. (2 * Pi roughly)

Edited by deleted (Tue 26-Jan-16 07:28:57)

Delving into the obscure again ....

In reply to a post by eckiedoo:

Why "0.772 MHz"?

This one continued to puzzle me.

A google search came up with this page:
https://en.wikipedia.org/wiki/High-bit-rate_digital_...

which, in turn, included this quote:

In reference to en.wikipedia.org/wiki/High-bit-rate_digital_subscriber_line:

The Nyquist frequency of a 1.544 megabaud signal is 772 kHz.

And that speed rumbles through my memory ... A 1.544 Mbps channel is commonly known as T1, and is the age-old standard in the US for carrying PCM-encoded speech - 24 channels of 64kbps. It dates back to the sixties.

Most of the rest of the world used E1, 30 channels of 64kbps, running at 2Mbp (ok - 2.048Mbps to be precise). It was very standard in the eighties, and is the basis of our System X and System Y exchanges.

I'm not an analog engineer, so while I understand that the Nyquist frequency has something to do with the carrying of digital data on analog systems, I don't understand the full ramifications. However, I'd be willing to bet that the fact American cabling standards choose to measure attenuation at 772kHz is because it indicates their suitability for carrying T1.

Having realised this, I could then find things like this, within a document on carrying T1 over twisted pairs:

In reference to ftp.tiaonline.org/TR-30/TR-30.3/Public/0012%20Scottsdale/0e140026%2...:

For the T1 line system, bipolar (AMI) encoding of the 1.544 Mbps signal results in a transmitted spectrum centered on 772 kHz.

Thanks again, WWWombat.

Amazing how far the OP's apparently simple question has taken us.

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Regarding the seven maximum, 1 inch cables in a 3.25 inch duct, after having slightly laboriously gone through drawing suitable circles in a graphics program etc, overnight it occurred to me that the "honeycomb" extended colour selection in such programs may be easier as a first approximation.

Checking that, certainly with one central hexagonal cell approximating to a circle, there are six on the next ring.

In reply to a post by eckiedoo:

Checking that, certainly with one central hexagonal cell approximating to a circle, there are six on the next ring.

And is why network planning for cellular networks regularly shows up with exactly this pattern of hexagons.

That pattern then dictates the frequency re-use pattern needed to avoid interference at the edges of cells - with frequencies often broken into groups of 7. Or used to, for GSM-style networks.

It seems it is a fully fledged cabinet, full of electronics and bolted now. Guy living next to it said it came in a wooden box and was full of wires!

In your photo, it still has lifting eyes attached.

I've never noticed that there must be 2 threaded holes at the top corner of each cab...

Edited by deleted (Tue 26-Jan-16 13:51:03)

Lifting eyes now gone and power connected! Also the big grey tube now runs to the manhole in front of the PCP. Assume that their must be enough duct space between the manhole and the cab behind it, as no new ducts installed into it.

I managed to get a quick look in the PCP on Friday,in poor weather. No camera to hand.

There were no obvious signs of the "blue cable" inside at the bottom right, where black, 1 inch, Link Cables were clearly coming in. Did not manage a count.

Will try to get more definite information, hopefully in better weather.

I now suspect that the "blue cable" doubling back in the U-G Chamber near the FTTC, is actually ducting rather than cabling, to accommodate the "up to six/three pairs" of black, 1 inch, Link Cables to serve the FTTC's full capacity of 288.

If the multiple Link Cables had been directly visible in that chamber, I think (and hope) I would have noted and remembered them.

Morning WWWombaT

I happened to notice that there is Blue Ducting in some of the photos on this site - so seemingly confirming that it is probably used for the multiple Link Cables-

http://fibre.everestpark.org.uk/2015/11/05/we-are-a-go/

In reply to a post by eckiedoo:

Morning WWWombaT

I happened to notice that there is Blue Ducting in some of the photos on this site - so seemingly confirming that it is probably used for the multiple Link Cables-

http://fibre.everestpark.org.uk/2015/11/05/we-are-a-go/

It's not blue. It's (telecom) grey.

Thanks Panda.

Reminiscent of when we supplied an early Numerical Control System in 1963 to Farnborough, as part of the early development for Concorde.

It had to be painted an MoD-specified colour, which was named some sort of "Grey".

When we obtained a sample swatch from British Standards, everyone's reaction was "Pea Green".

Can you confirm or otherwise that it is for the Link Cables joining the PCP and the FTTC?

http://www.coolwebhome.co.uk/fibre-cornwall/images/f...

Same ducting, and yes its called grey, colour issues on camera may not help.

Fibres in one and the other has the copper going into it, with the attendant waterproof seal.

When everyone was talking about blue I thought you meant the blue pull ropes that are often visible.

I was looking at the photo's you provided, thinking "They're grey. Aren't they?"

Is this another case of The Dress?

Blown up, that becomes a very good picture of the fibre capability too.

It looks to me like there is space for 8 separate fibres - with 8 yellow fibres running between the two compartments, and most of the connectors left dangling. In the DSLAM, the card in use has 1 of 4 slots used. However, to the left of that card there looks to be 2 others that have angled slots for optical modules.