Small estate on edge of a village, van and 3 chaps stringing a cable along
the telegraph poles. Cable was about 6mm dia., black with a yellow stripe
along it.
Any idea what it is? I'm assuming frome the diameter and low flxibility
(there were a couple of loose coils taking up a lot of the footway and the
bit being handled wasn't floppy like flex) that it's possibly FTTP. The van
didn't have any markings on it.
--
Peter.
The gods will stay away
whilst religions hold sway

On 14/10/2020 16:16, PeterC wrote:
Small estate on edge of a village, van and 3 chaps stringing a cable along
the telegraph poles. Cable was about 6mm dia., black with a yellow stripe
along it.
Any idea what it is? I'm assuming frome the diameter and low flxibility
(there were a couple of loose coils taking up a lot of the footway and the
bit being handled wasn't floppy like flex) that it's possibly FTTP. The van
didn't have any markings on it.


Thats the container for fibre, which is already inside it.

On 14/10/2020 16:16, PeterC wrote:
Small estate on edge of a village, van and 3 chaps stringing a cable along
the telegraph poles. Cable was about 6mm dia., black with a yellow stripe
along it.

Yellow stripe usually indicates fibre. (and the cable "recyclers" have
been educated that any time they see yellow stripes or cable flags there
is no scrap value for it!)

Here is a termination point near us before any customers were hooked up
to it - you can see the yellow stripe cable:

http://wiki.diyfaq.org.uk/index.php/...ermination.jpg

Any idea what it is? I'm assuming frome the diameter and low flxibility
(there were a couple of loose coils taking up a lot of the footway and the
bit being handled wasn't floppy like flex) that it's possibly FTTP. The van
didn't have any markings on it.

Probably a sub contractor for openreach.


--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

On Thu, 15 Oct 2020 09:45:46 +0100, John Rumm wrote:

On 14/10/2020 16:16, PeterC wrote:
Small estate on edge of a village, van and 3 chaps stringing a cable along
the telegraph poles. Cable was about 6mm dia., black with a yellow stripe
along it.

Yellow stripe usually indicates fibre. (and the cable "recyclers" have
been educated that any time they see yellow stripes or cable flags there
is no scrap value for it!)

Here is a termination point near us before any customers were hooked up
to it - you can see the yellow stripe cable:

http://wiki.diyfaq.org.uk/index.php/...ermination.jpg

Is it run to a DP and then to the properties, same as copper is? Certainly
save digging.

--
Peter.
The gods will stay away
whilst religions hold sway

On Thu, 15 Oct 2020 15:17:52 +0100, PeterC wrote:

Here is a termination point near us before any customers were
hooked up
to it - you can see the yellow stripe cable:

http://wiki.diyfaq.org.uk/index.php/...ermination.jpg

That's a joint bullet where one cable is split to two others (in this
case).

Is it run to a DP and then to the properties, same as copper is?
Certainly save digging.

After the split the cables will run to a fibre DP at the top of a
pole or maybe another split. The fibre DPs are black with quite
chunky downward pointing prongs. These are individual fibre ports
fitted with a blanking plug. To connect a customer the blanking plug
is removed and the cable plugged in, the blanking plug then mated
with the cables cap to keep things clean. Fibre cable run to premises
and a fibre connector fitted to plug into the ONT.

--
Cheers
Dave.

On 15/10/2020 15:17, PeterC wrote:
On Thu, 15 Oct 2020 09:45:46 +0100, John Rumm wrote:

On 14/10/2020 16:16, PeterC wrote:
Small estate on edge of a village, van and 3 chaps stringing a cable along
the telegraph poles. Cable was about 6mm dia., black with a yellow stripe
along it.

Yellow stripe usually indicates fibre. (and the cable "recyclers" have
been educated that any time they see yellow stripes or cable flags there
is no scrap value for it!)

Here is a termination point near us before any customers were hooked up
to it - you can see the yellow stripe cable:

http://wiki.diyfaq.org.uk/index.php/...ermination.jpg

Is it run to a DP and then to the properties, same as copper is? Certainly
save digging.

Round here its all on poles, so no digging required, just a drop cable
from the pole direct to the house.


--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

On Thu, 15 Oct 2020 16:34:26 +0100 (BST), Dave Liquorice wrote:

On Thu, 15 Oct 2020 15:17:52 +0100, PeterC wrote:

Here is a termination point near us before any customers were
hooked up
to it - you can see the yellow stripe cable:

http://wiki.diyfaq.org.uk/index.php/...ermination.jpg

That's a joint bullet where one cable is split to two others (in this
case).

Is it run to a DP and then to the properties, same as copper is?
Certainly save digging.

After the split the cables will run to a fibre DP at the top of a
pole or maybe another split. The fibre DPs are black with quite
chunky downward pointing prongs. These are individual fibre ports
fitted with a blanking plug. To connect a customer the blanking plug
is removed and the cable plugged in, the blanking plug then mated
with the cables cap to keep things clean. Fibre cable run to premises
and a fibre connector fitted to plug into the ONT.

Thanks for the explanation. I'll see if it has made any progress next time
I'm passing.
FTTP might not be very good here. We get a steady 37Mbps down 9Mbps up and
that's it on FTTC. The cabinet is about 3km from the exchange; I don't know
if that is a factor with fibre.
--
Peter.
The gods will stay away
whilst religions hold sway

PeterC wrote:

The cabinet is about 3km from the exchange; I don't know
if that is a factor with fibre.

58 km limit I believe.

On 16/10/2020 09:32, PeterC wrote:
We get a steady 37Mbps down 9Mbps up and
that's it on FTTC. The cabinet is about 3km from the exchange; I don't know
if that is a factor with fibre.

The length of the copper between you and the cabinet is the important
factor.

On 16/10/2020 09:32, PeterC wrote:
On Thu, 15 Oct 2020 16:34:26 +0100 (BST), Dave Liquorice wrote:

On Thu, 15 Oct 2020 15:17:52 +0100, PeterC wrote:

Here is a termination point near us before any customers were
hooked up
to it - you can see the yellow stripe cable:

http://wiki.diyfaq.org.uk/index.php/...ermination.jpg

That's a joint bullet where one cable is split to two others (in this
case).

Is it run to a DP and then to the properties, same as copper is?
Certainly save digging.

After the split the cables will run to a fibre DP at the top of a
pole or maybe another split. The fibre DPs are black with quite
chunky downward pointing prongs. These are individual fibre ports
fitted with a blanking plug. To connect a customer the blanking plug
is removed and the cable plugged in, the blanking plug then mated
with the cables cap to keep things clean. Fibre cable run to premises
and a fibre connector fitted to plug into the ONT.

Thanks for the explanation. I'll see if it has made any progress next time
I'm passing.

FTTP might not be very good here.

FTTP is one of those things that generally works or doesn't - there is
no practical variability in performance with distance.

We get a steady 37Mbps down 9Mbps up and
that's it on FTTC.

Is that on a 80/20 or 40/10 service? Assuming the latter, it would
indicate you are relatively close to the cabinet (under 1km)

The cabinet is about 3km from the exchange;

That is not the metric that matters - the connection from cabinet to
exchange will be fibre, and not particularly distance sensitive. What
matters is the length of the copper wiring that has to run VDSL from the
cabinet to the end user. So within a few hundred meters it will run flat
out. Over than and it degrades with distance. Once you are over a few
km, then performance will be down in the low single Mbit range, and
probably no better than with ADSL.

I don't know
if that is a factor with fibre.

Fibre does have distance limits - but those are "per segment" so you can
extend by adding another repeater and another segment. So its much
better suited to long runs out into the middle of nowhere.


--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

On Fri, 16 Oct 2020 09:37:04 +0100, Andy Burns wrote:

The cabinet is about 3km from the exchange; I don't know
if that is a factor with fibre.

For FTTC it's the length and condition of the copper from the cabinet
to you that is important. With 37 Mbps down that equates to about 700
m.

58 km limit I believe.

That's certainly within the range of a single mode fibre point to
point link but I think Openreach are installing GPON (Gigabit Passive
Optical Network). This takes the fibre from the head end "line card"
and optically splits it 32 (or even 64) ways. This reduces the range
but it's still in the order of 10 km or more providing up to 1 Gbps
symetrical (if they wanted to).

--
Cheers
Dave.

On Fri, 16 Oct 2020 10:10:25 +0100, John Rumm wrote:

... the connection from cabinet to exchange will be fibre, and not
particularly distance sensitive.

And almost certainly not the same exchange that the POTS copper pair
goes to. When they installed FTTC here they also installed a new
fibre cable for them all the way from Hexham 40 km away. Yes, they
did have trouble with light levels on a couple of them.

Once you are over a few km, then performance will be down in the low
single Mbit range, and probably no better than with ADSL.

Openreach won't market FTTC lines as such unless they are pretty sure
that they will support "superfast" broadband, ie 24 Mbps down. Our
line is one such, it goes through "VDSL cabinet" but at the exchange
about 4 km away so we are stuck with ADSL2+, which is currently doing
very well. 7611 kbps down sync with a 6.1 dB S/N ratio.

Fibre does have distance limits - but those are "per segment" so you can
extend by adding another repeater and another segment. So its much
better suited to long runs out into the middle of nowhere.

Even the the longest runs from the exchange out here at 7 miles (11
km) are probably within the range of FTTP with the optical split at
the head end (it doesn't have to be...).

--
Cheers
Dave.

On 16/10/2020 09:37, Andy Burns wrote:
PeterC wrote:

The cabinet is about 3km from the exchange; I don't know
if that is a factor with fibre.

58 km limit I believe.

VERY dependeent on a lot of factors. But I agree 'tens of kilometers' is
in the ball park for cooking grade monomode.



--
"In our post-modern world, climate science is not powerful because it is
true: it is true because it is powerful."

Lucas Bergkamp

On 16/10/2020 10:14, Dave Liquorice wrote:
On Fri, 16 Oct 2020 09:37:04 +0100, Andy Burns wrote:

The cabinet is about 3km from the exchange; I don't know
if that is a factor with fibre.

For FTTC it's the length and condition of the copper from the cabinet
to you that is important. With 37 Mbps down that equates to about 700
m.

58 km limit I believe.

That's certainly within the range of a single mode fibre point to
point link but I think Openreach are installing GPON (Gigabit Passive
Optical Network). This takes the fibre from the head end "line card"
and optically splits it 32 (or even 64) ways. This reduces the range
but it's still in the order of 10 km or more providing up to 1 Gbps
symetrical (if they wanted to).

yes, and no. You have described what the Open Reach engineer said
happened (optical splitting), but he said the fibre went 10 + miles to a
big exchange, and could do more than that. It is really probably about
the amount of *power* that can be sent down it - the splitter is a
different sort of loss from a long fibre, in that its probably a flat
loss across the band, not a load of frequency dependent phase shifts.

The limit of multimode is reached when all the different paths combine
to give a mess of incoherent phases, not because the signal is too low.
For example.

This may be of interest:

"As we all know, multimode fiber is usually divided into OM1, OM2, OM3,
OM4 and OM5 fiber types. When it comes to single mode fiber types, it
can be categorized into OS1 and OS2 fiber, which are SMF fiber
specifications. OS1 and OS2 are standard single mode optical cables
respectively used with wavelengths of 1310nm and 1550nm with a maximum
attenuation of 1 dB/km and 0.4 dB/km. OS1 fiber is a tight buffered
cable designed for use in indoor applications (such as campuses or data
centers) where the maximum distance is 10 km. OS2 fiber is a loose tube
cable designed for use in outdoor cases (like street, underground and
burial) where the maximum distance is *up to 200 km*. Both OS1 and OS2
fiber optic cable support Gigabit and 10G Ethernet links. "


Certainly undersea repeaters are over 100km apart if possible.

And thinking about the splitter, that represents only really a 20 db
loss for 100 way split...and provided the power is there that's no big
loss.

It probably represents no more than a third of the usable length being lost.

--
In todays liberal progressive conflict-free education system, everyone
gets full Marx.

On 16 Oct 2020 09:52:15 GMT, Tim Streater wrote:

If you use expensive optical kit, you can use 96 different wavelengths
on a SM fibre with, IIRC, 100GHz separation. That allows 10Gbps per
channel, although they probably do 40Gbps these days. That's for
backbone networks, and was what we were doing when I retired. Dunno what
they can do these days.

Maybe DWDM (Dense Wavelength Division Multiplexing) seems that can
support 192 channels at 100 Gbps/channel giving 19.2 Tbps over a
single fibre pair. Openreach used 96 core cable to feed the FTTC
boxes around here. Zayo have recently installed a 144 core cable
between Penrith and Hexham.

144/2 * 91.2 = 1382.4 Tbps

--
Cheers
Dave.

On Fri, 16 Oct 2020 15:02:36 +0100, The Natural Philosopher wrote:

... but I think Openreach are installing GPON (Gigabit Passive
Optical Network). This takes the fibre from the head end "line
card"
and optically splits it 32 (or even 64) ways. This reduces the
range
but it's still in the order of 10 km or more providing up to 1
Gbps
symetrical (if they wanted to).

yes, and no. You have described what the Open Reach engineer said
happened (optical splitting), but he said the fibre went 10 + miles to a
big exchange, and could do more than that.

Pre or post the optical split? The unsplit headend feed is quite
"pokey" and can do considerable distances without amplification, 40
km from here to Hexham for example.

It is really probably about the amount of *power* that can be sent down
it - the splitter is a different sort of loss from a long fibre, in that
its probably a flat loss across the band, not a load of frequency
dependent phase shifts.

The limit of multimode ...

Are Openreach using multimode? Singlemode has a far greater range and
doesn't mess up the signal(s). I don't think DWDM would work over
multimode. I think GPON only uses two "carriers", (up/down), within a
single fibre and uses TDM to share those two carriers between
customers. That might work over multimode but for how far I don't
know.

As you say the range of singlemode is really down to how bright (ie
power) you can make the source laser. Powers are such that caution
needs to be applied to protect your eyes when working on such sytems.
You can't see the IR laser light.

--
Cheers
Dave.

On 16/10/2020 23:58, Dave Liquorice wrote:
On Fri, 16 Oct 2020 15:02:36 +0100, The Natural Philosopher wrote:

... but I think Openreach are installing GPON (Gigabit Passive
Optical Network). This takes the fibre from the head end "line
card"
and optically splits it 32 (or even 64) ways. This reduces the
range
but it's still in the order of 10 km or more providing up to 1
Gbps
symetrical (if they wanted to).

yes, and no. You have described what the Open Reach engineer said
happened (optical splitting), but he said the fibre went 10 + miles to a
big exchange, and could do more than that.

Pre or post the optical split? The unsplit headend feed is quite
"pokey" and can do considerable distances without amplification, 40
km from here to Hexham for example.

I think it probably makes no difference.
If my thinking is about right, the splitter simply represents - say - a
20dB loss in the path no matter where it is, in fact.

If, let's say, we have 60dB of headroom, and the attenuation is 1 db per
km, with no splitter that's 60km, with one splitter its 40km and with
two its 20km.

And so on.


It is really probably about the amount of *power* that can be sent down
it - the splitter is a different sort of loss from a long fibre, in that
its probably a flat loss across the band, not a load of frequency
dependent phase shifts.

The limit of multimode ...

Are Openreach using multimode? Singlemode has a far greater range and
doesn't mess up the signal(s). I don't think DWDM would work over
multimode. I think GPON only uses two "carriers", (up/down), within a
single fibre and uses TDM to share those two carriers between
customers. That might work over multimode but for how far I don't
know.

No, they (Openrach) are not, I cited that as a counter example, where
high dispersion limits practical length to 'not very far'. I think
monomode is limited by optical attenuation, not dispersion.

As you say the range of singlemode is really down to how bright (ie
power) you can make the source laser. Powers are such that caution
needs to be applied to protect your eyes when working on such systems.
You can't see the IR laser light.

They are IR? I know there are standard wavelengths - dont know what they
are, though..

--
"I guess a rattlesnake ain't risponsible fer bein' a rattlesnake, but ah
puts mah heel on um jess the same if'n I catches him around mah chillun".

On Sat, 17 Oct 2020 09:13:42 +0100, The Natural Philosopher wrote:

yes, and no. You have described what the Open Reach engineer said
happened (optical splitting), but he said the fibre went 10 +
miles to
a big exchange, and could do more than that.

Pre or post the optical split? The unsplit headend feed is quite
"pokey" and can do considerable distances without amplification,
40
km from here to Hexham for example.

I think it probably makes no difference.
If my thinking is about right, the splitter simply represents - say - a
20dB loss in the path no matter where it is, in fact.

If, let's say, we have 60dB of headroom, and the attenuation is 1 db per
km, with no splitter that's 60km, with one splitter its 40km and with
two its 20km.

Good point, well made. Of course having the split further away means
you have combined all 32 (or WHY) customer fibres into one.
I think monomode is limited by optical attenuation, not dispersion.

Yes, the light travels straight down the core of fibre rather than
being reflected of the sides which causes different path lengths for
individual photons and thus what starts as tight pulse of photons
ends up spread out over time at a given point some distance away.


Powers are such that caution needs to be applied to protect your eyes
when working on such systems. You can't see the IR laser light.

They are IR? I know there are standard wavelengths - dont know what they
are, though..

There's about half a dozen standard wavelengths used across multimode
and single mode fibre. Around 1550 nm is one of wavelengths used by
singlemode. IR starts just below visible red at 700 ish nm and goes
to about 1 mm.

--
Cheers
Dave.

On 17/10/2020 16:13, Dave Liquorice wrote:
Yes, the light travels straight down the core of fibre rather than
being reflected of the sides which causes different path lengths for
individual photons and thus what starts as tight pulse of photons
ends up spread out over time at a given point some distance away.

If I didn't know I'd be confused by that...

Fibres are made of two different types of glass. On multimode the
boundary between them acts as a mirror; on single mode they are blended
so the boundary acts as a lens and gently steers the beam even when
there is a bend in the cable.

Or something like that. I'm no physicist.

Andy

On 18/10/2020 21:37, Vir Campestris wrote:
On 17/10/2020 16:13, Dave Liquorice wrote:
Yes, the light travels straight down the core of fibre rather than
being reflected of the sides which causes different path lengths for
individual photons and thus what starts as tight pulse of photons
ends up spread out over time at a given point some distance away.

If I didn't know I'd be confused by that...

Fibres are made of two different types of glass. On multimode the
boundary between them acts as a mirror; on single mode they are blended
so the boundary acts as a lens and gently steers the beam even when
there is a bend in the cable.

Or something like that. I'm no physicist.

You are describing what are known as "graded index" and "step index"
fibres. (Monomode and multimode can be made using both types, although
the graded index cause less modal dispersion).

Monomode tend to use a much thinner core (and are usually step index as
there are not many advantages to using graded index for monomode - but
its more difficult to manufacture), so that they can basically only
accept one incident angle of light entry.


--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

On Monday, 19 October 2020 02:06:49 UTC+1, John Rumm wrote:
On 18/10/2020 21:37, Vir Campestris wrote:
On 17/10/2020 16:13, Dave Liquorice wrote:
Yes, the light travels straight down the core of fibre rather than
being reflected of the sides which causes different path lengths for
individual photons and thus what starts as tight pulse of photons
ends up spread out over time at a given point some distance away.

If I didn't know I'd be confused by that...

Fibres are made of two different types of glass. On multimode the
boundary between them acts as a mirror; on single mode they are blended
so the boundary acts as a lens and gently steers the beam even when
there is a bend in the cable.

Or something like that. I'm no physicist.

You are describing what are known as "graded index" and "step index"
fibres. (Monomode and multimode can be made using both types, although
the graded index cause less modal dispersion).

Monomode tend to use a much thinner core (and are usually step index as
there are not many advantages to using graded index for monomode - but
its more difficult to manufacture), so that they can basically only
accept one incident angle of light entry.

If you bend a fibre some of the light leaks out. A couple of weeks ago I
watched a fibre leased line being installed. The installers had a very
nice tone tracer for fibre. The fibre (encased in its coloured protective
plastic sheath) was pushed into a curved slot which bent it, causing
enough light to leak out that they could monitor traffic and play an
audible tone if a pulsed laser was attached to one end of the fibre.
The bend radius looked like 2 or 3cm.

John

wrote:

If you bend a fibre some of the light leaks out. A couple of weeks ago I
watched a fibre leased line being installed.
The bend radius looked like 2 or 3cm.

When I hired a fluke fibre tester, it came with a small "mandrel" about
that diameter which you wrapped a few turns of the fibre around for
testing, I think it was to attenuate the light that had taken a highly
reflected path through the fibre and only measure the more direct paths?