From the new dumbed-down Torygraph.

http://www.telegraph.co.uk/technolog...aunches-giant-
undersea-internet-cable/

"Although the optical fibres that transport data are extremely thin, the
cables have to be reinforced with layers of tubing, steel wires and
plastic to prevent damage. The cables have become a target for shark
attacks, with sharks possibly drawn to the electromagnetic signals
running through them"

Um...

--
(\_/)
(='.'=) systemd: the Linux version of Windows 10
(")_(")

On 02/07/2016 16:35, Mike Tomlinson wrote:

From the new dumbed-down Torygraph.

http://www.telegraph.co.uk/technolog...aunches-giant-
undersea-internet-cable/

"Although the optical fibres that transport data are extremely thin, the
cables have to be reinforced with layers of tubing, steel wires and
plastic to prevent damage. The cables have become a target for shark
attacks, with sharks possibly drawn to the electromagnetic signals
running through them"

Are you absolutely sure there aren't optical repeaters, in which case
currents might flow in the sheath?

I would still expect copper cables within the steel reinforcing to
supply the power.

On 02/07/16 16:41, Fredxxx wrote:
On 02/07/2016 16:35, Mike Tomlinson wrote:

From the new dumbed-down Torygraph.

http://www.telegraph.co.uk/technolog...aunches-giant-
undersea-internet-cable/

"Although the optical fibres that transport data are extremely thin, the
cables have to be reinforced with layers of tubing, steel wires and
plastic to prevent damage. The cables have become a target for shark
attacks, with sharks possibly drawn to the electromagnetic signals
running through them"

Are you absolutely sure there aren't optical repeaters, in which case
currents might flow in the sheath?

I would still expect copper cables within the steel reinforcing to
supply the power.

There most definitely are repeaters, cos I worked on the design of one,
and yes, sharks do get attracted to the currents



--
Ideas are more powerful than guns. We would not let our enemies have
guns, why should we let them have ideas?

Josef Stalin

On 02/07/2016 16:35, Mike Tomlinson wrote:

From the new dumbed-down Torygraph.

http://www.telegraph.co.uk/technolog...aunches-giant-
undersea-internet-cable/

"Although the optical fibres that transport data are extremely thin, the
cables have to be reinforced with layers of tubing, steel wires and
plastic to prevent damage. The cables have become a target for shark
attacks, with sharks possibly drawn to the electromagnetic signals
running through them"

Um...


What do you think is incorrect?

Mike Tomlinson wrote:

http://www.telegraph.co.uk/technolog...aunches-giant-
undersea-internet-cable/

"Although the optical fibres that transport data are extremely thin, the
cables have to be reinforced with layers of tubing, steel wires and
plastic to prevent damage. The cables have become a target for shark
attacks, with sharks possibly drawn to the electromagnetic signals
running through them"

Um...

Power for the repeaters?

En el artículo , Andy Burns
escribió:

Power for the repeaters?

A few amps. And the cable's shielded by armour. Several times.

--
(\_/)
(='.'=) systemd: the Linux version of Windows 10
(")_(")

On Sat, 2 Jul 2016 16:50:47 +0100, dennis@home
wrote:

On 02/07/2016 16:35, Mike Tomlinson wrote:

From the new dumbed-down Torygraph.

http://www.telegraph.co.uk/technolog...aunches-giant-
undersea-internet-cable/

"Although the optical fibres that transport data are extremely thin, the
cables have to be reinforced with layers of tubing, steel wires and
plastic to prevent damage. The cables have become a target for shark
attacks, with sharks possibly drawn to the electromagnetic signals
running through them"

Um...


What do you think is incorrect?

He doesn't know. He doesn't realise just how thick he is.

No wonder he wanted to talk about angle grinders (not that he's ever
used one). [1]

Cheers, T i m

[1] Then starts a thread about something else non d-i-y.

Mike Tomlinson wrote:

Andy Burns wrote:

Power for the repeaters?

A few amps. And the cable's shielded by armour. Several times.

Maybe the armour doubles as a conductor?

En el artículo , Andy Burns
escribió:
Mike Tomlinson wrote:

Andy Burns wrote:

Power for the repeaters?

A few amps. And the cable's shielded by armour. Several times.

Maybe the armour doubles as a conductor?

With the sea as a return? Possibly. It'd save the cost running
separate power wires alongside the fibre. That, or run one core and use
the armour as the return.

--
(\_/)
(='.'=) systemd: the Linux version of Windows 10
(")_(")

On 02/07/16 17:44, Andy Burns wrote:
Mike Tomlinson wrote:

Andy Burns wrote:

Power for the repeaters?

A few amps. And the cable's shielded by armour. Several times.

Maybe the armour doubles as a conductor?


AKAIC the outer armour is 'earth' and an inner copper tube that carries
the fibres, or a discrete wire, powers the repeaters in series down the
cable.


--
"When a true genius appears in the world, you may know him by this sign,
that the dunces are all in confederacy against him."

Jonathan Swift.

On Saturday, 2 July 2016 16:35:41 UTC+1, Mike Tomlinson wrote:
From the new dumbed-down Torygraph.

http://www.telegraph.co.uk/technolog...aunches-giant-
undersea-internet-cable/

"Although the optical fibres that transport data are extremely thin, the
cables have to be reinforced with layers of tubing, steel wires and
plastic to prevent damage. The cables have become a target for shark
attacks, with sharks possibly drawn to the electromagnetic signals
running through them"

Um...

--
(\_/)
(='.'=) systemd: the Linux version of Windows 10
(")_(")

Sharks in common with many fish have very sensitive electric field sensors.
So sensitive they can pick up the electrical activity generated by nerve signals of their prey (eg buried in mud)
So, it's very possible.
http://www.pelagic.org/overview/articles/sixsense.html

On 02/07/2016 17:59, The Natural Philosopher wrote:
On 02/07/16 17:44, Andy Burns wrote:
Mike Tomlinson wrote:

Andy Burns wrote:

Power for the repeaters?

A few amps. And the cable's shielded by armour. Several times.

Maybe the armour doubles as a conductor?


AKAIC the outer armour is 'earth' and an inner copper tube that carries
the fibres, or a discrete wire, powers the repeaters in series down the
cable.

I assumed the repeaters were powered in series.

The Natural Philosopher wrote:

Andy Burns wrote:

Maybe the armour doubles as a conductor?

AKAIC the outer armour is 'earth' and an inner copper tube that carries
the fibres, or a discrete wire, powers the repeaters in series down the
cable.

I've heard that sharks can detect an AA battery carried by divers, so
any stray voltage might well 'interest' them ...

En el artículo , Fredxxx
escribió:

I assumed the repeaters were powered in series.

So when one goes bang it's time to play the traditional Christmas game
of "find the blown bulb?"



--
(\_/)
(='.'=) systemd: the Linux version of Windows 10
(")_(")

On 02/07/16 19:05, Mike Tomlinson wrote:
En el artÃ*culo , Fredxxx
escribió:

I assumed the repeaters were powered in series.

So when one goes bang it's time to play the traditional Christmas game
of "find the blown bulb?"


Very much so.

Then out go the grapplers to try and snag the cable






--
Karl Marx said religion is the opium of the people.
But Marxism is the crack cocaine.

On Sat, 2 Jul 2016 16:35:34 +0100
Mike Tomlinson wrote:

From the new dumbed-down Torygraph.

http://www.telegraph.co.uk/technolog...aunches-giant-
undersea-internet-cable/

"Although the optical fibres that transport data are extremely thin,
the cables have to be reinforced with layers of tubing, steel wires
and plastic to prevent damage. The cables have become a target for
shark attacks, with sharks possibly drawn to the electromagnetic
signals running through them"

You have to remember that sharks can smell your thoughts.
:-)


















































"Sharks are the most electrically sensitive animals known, responding to
DC fields as low as 5 nV/cm."

On 02/07/2016 17:31, T i m wrote:
On Sat, 2 Jul 2016 16:50:47 +0100, dennis@home
wrote:

On 02/07/2016 16:35, Mike Tomlinson wrote:

From the new dumbed-down Torygraph.

http://www.telegraph.co.uk/technolog...aunches-giant-
undersea-internet-cable/

"Although the optical fibres that transport data are extremely thin, the
cables have to be reinforced with layers of tubing, steel wires and
plastic to prevent damage. The cables have become a target for shark
attacks, with sharks possibly drawn to the electromagnetic signals
running through them"

Um...


What do you think is incorrect?

He doesn't know. He doesn't realise just how thick he is.

Could you two love birds go have a tiff elsewhere?

--
Cheers,

John.

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

On 02/07/2016 19:05, Mike Tomlinson wrote:
En el artículo , Fredxxx
escribió:

I assumed the repeaters were powered in series.

So when one goes bang it's time to play the traditional Christmas game
of "find the blown bulb?"

If they were in parallel are you suggesting that finding the offending
failed repeater would be simpler?

Are you advocating there is trail of lights on the sea bed or something?

This thread and your responses aren't doing you any favours.

On Sat, 2 Jul 2016 20:04:39 +0100, John Rumm
wrote:

snip

He doesn't know. He doesn't realise just how thick he is.

Could you two love birds go have a tiff elsewhere?

;-)

Unfortunately, to have 'a tiff' you don't normally have one person
willing to discuss reasonably and the other running away and hiding?

That's just called 'someone throwing their toys out the pram'.

OOI, I didn't notice if you *also* stepped in when Tomlinson
gratuitously insults me from behind his cowardly killfile (I apologise
if you did).

Cheers, T i m

On Sat, 02 Jul 2016 17:59:19 +0100, Mike Tomlinson wrote:

En el artÃ*culo , Andy Burns
escribió:
Mike Tomlinson wrote:

Andy Burns wrote:

Power for the repeaters?

A few amps. And the cable's shielded by armour. Several times.

Maybe the armour doubles as a conductor?

With the sea as a return? Possibly. It'd save the cost running
separate power wires alongside the fibre. That, or run one core and use
the armour as the return.

Using the sea water as a 'Ground return' is a non-starter in this case.
ISTR seeing a reference to the power requirements for the TAT undersea
cables requiring 7Kv feeds from each end (positive at one end, negative
at the other - a grand total of 14KV in all to power the repeaters which
AFAICR were spaced at 2Km intervals, extracting some 20 to 30 volts off
the line to power the repeaters which had been designed at the GPO (now
BT)'s research establishment (Dollis Hill, Martlesham) using the special
long life transistors that had also been developed there).

Unless I'm many miles out, I figured a total route length approximating
to some 4,800Km, implying a total of 2,400 undersea repeaters. Even
assuming 20v per repeater, a simple series arrangement would have
demanded a total supply voltage of 48Kv (24KV at each end, way higher
than the 7KV figure I recalled). Possibly the 20 or 30 volt drops were
shared between 3 repeaters at a time with the section of centre conductor
between each trio acting as a common bus bar supply.

In either case, such very long undersea cable routes would require power
feeding of the amplifiers (old analogue system) or regenerator/laser
amplifiers (today's modern optical fibre systems) where several kilovolts
are applied at each end of the power conductors (centre conductor of each
co-axial tube in the old analogue FDM days with the outer tube shield/
return acting as the ground return for the DC supply which neatly nulled
out any magnetic leakage which might attract the attentions of deep sea
sharks) so that each amplifier/regenerator could tap voltage off the
constant current supplied from each shore station.

Effectively, each repeater (or group of repeaters)'s power connections
are in series with each other rather like the heater strings in the early
valved (tubed) TV sets to minimise inefficiency in powering 6 to 12v (or
even higher?) 300mA valve heaters off a 120 or 240 volt mains supply in
the absence of an expensively screened and weighty mains transformer.

I should imagine that a modern undersea optical fibre cable would use an
outer screening conductor as the ground return for the DC power to effect
cancellation of magnetic field leakage. Whether this would rely on the
outer stainless steel armouring to supplement a copper tube screen ground
or simply as a ground return conductor in its own right, I couldn't say
but it's odds on that such a co-axial conductor power feeding arrangement
would be use whatever the technology of the repeaters simply to eliminate
any emanation of magnetic flux from the cable.

Although the use of good quality stainless steel in the armouring of
such under sea cables should eliminate distortions in the local magnetic
field, it's possible that the shark's electro senses may still be
detecting the cable's presence, especially in sections of the route where
the cable crosses trenches or depressions in the ocean floor's topology
where it will form a catenary suspension above the ocean floor to occupy
the space where sharks would be freely swimming and more likely to detect
the slightest of such anomalies. Sections of undersea cable lying on the
sea floor, perhaps sunk into mud or soft sand, will be largely screened
from such electro detection by sharks.

In view of the above, it's perhaps not surprising that the reporter
glossed over the complexities of modern undersea cables when describing
why sharks might have been attracted to the cable(s) and taking
exploratory nibbles out of this potential food source.

--
Johnny B Good

En el artículo , Fredxxx
escribió:

If they were in parallel are you suggesting that finding the offending
failed repeater would be simpler?

**** me, sense of humour failure there.

Are you advocating there is trail of lights on the sea bed or something?

**** me, taking things literally.

This thread and your responses aren't doing you any favours.

I think it shows you up for the humourless literal **** you are. Or are
you suggesting fibre optics emit electromagnetic waves?

Go and bore someone else.

--
(\_/)
(='.'=) systemd: the Linux version of Windows 10
(")_(")

On Sat, 02 Jul 2016 18:49:11 +0100, Fredxxx wrote:

On 02/07/2016 17:59, The Natural Philosopher wrote:
On 02/07/16 17:44, Andy Burns wrote:
Mike Tomlinson wrote:

Andy Burns wrote:

Power for the repeaters?

A few amps. And the cable's shielded by armour. Several times.

Maybe the armour doubles as a conductor?


AKAIC the outer armour is 'earth' and an inner copper tube that carries
the fibres, or a discrete wire, powers the repeaters in series down the
cable.

I assumed the repeaters were powered in series.

That's basically the method though the 20 to 30 volts drop might have
been shared to repeaters in clusters of 3 or 4 at a time. Modern kit
using regenerator/laser amplifiers may be able to manage on less voltage,
plus the repeater spacing on fibre links can be an order or two greater
than the 2Km spacing that was once used on undersea co-axial cables using
analogue RF amplifiers back in the days of FDM. The shorter undersea
fibre optic routes of 100Km or so can manage without resorting to
undersea repeaters.

On longer, trans-oceanic routes measuring several thousand kilometres,
each end of the cable would be fed with an HT DC voltage measuring
several Kilovolts! (7KV at each end of the TAT cables being laid down in
the late 70s / early 80s afair - positive one end and negative the other
to provide a total of 14Kv over co-axial cable that didn't need to be
rated for the full 14Kv).

--
Johnny B Good

"Mike Tomlinson" wrote in message
...

From the new dumbed-down Torygraph.

http://www.telegraph.co.uk/technolog...aunches-giant-
undersea-internet-cable/

"Although the optical fibres that transport data are extremely thin, the
cables have to be reinforced with layers of tubing, steel wires and
plastic to prevent damage. The cables have become a target for shark
attacks, with sharks possibly drawn to the electromagnetic signals
running through them"

Um...

Pity about what powers the repeaters.

"Fredxxx" wrote in message
...
On 02/07/2016 19:05, Mike Tomlinson wrote:
En el artículo , Fredxxx
escribió:

I assumed the repeaters were powered in series.

So when one goes bang it's time to play the traditional Christmas game
of "find the blown bulb?"

If they were in parallel are you suggesting that finding the offending
failed repeater would be simpler?

Corse it would be when all but the failed one would still be working.

Are you advocating there is trail of lights on the sea bed or something?

Yes, or something.

This thread and your responses aren't doing you any favours.

On Sun, 3 Jul 2016 09:35:18 +1000, Jacky Chance wrote:

The cables have become a target for shark attacks, with sharks
possibly
drawn to the electromagnetic signals running through them"

Um...

Pity about what powers the repeaters.

They might be using light for that as well. I know it's been
researched and they could get a useable amount of power at the
reciving end. Don't think it was very effcient though but things
could have improved.

--
Cheers
Dave.

"Jacky Chance" wrote in message
...

"Rod Speed" wrote in message
...

"Dave Liquorice" wrote in message
idual.net...
On Sun, 3 Jul 2016 09:35:18 +1000, Jacky Chance wrote:

The cables have become a target for shark attacks, with sharks
possibly
drawn to the electromagnetic signals running through them"

Um...

Pity about what powers the repeaters.

They might be using light for that as well.

No they don't on that particular cable.

I know it's been
researched and they could get a useable amount of power at the
reciving end.

I don't believe that with a cable anything like that
long with the number of repeaters that cable uses.

Don't think it was very effcient though but things
could have improved.

No they have not. There is nothing like enough light to do that.

On 02/07/16 20:50, Johnny B Good wrote:
the complexities of modern undersea cables when describing
why sharks might have been attracted to the cable(s) and taking
exploratory nibbles out of this potential food source.

Every so often I see a really fascinating USENET post which reminds me
why I spend so much time on t'interweb. This was one of them; thank you.

--

Henry Law Manchester, England

Johnny B Good wrote:
On Sat, 02 Jul 2016 17:59:19 +0100, Mike Tomlinson wrote:

En el artÃ*culo , Andy Burns
escribió:
Mike Tomlinson wrote:

Andy Burns wrote:

Power for the repeaters?
A few amps. And the cable's shielded by armour. Several times.
Maybe the armour doubles as a conductor?
With the sea as a return? Possibly. It'd save the cost running
separate power wires alongside the fibre. That, or run one core and use
the armour as the return.

Using the sea water as a 'Ground return' is a non-starter in this case.
ISTR seeing a reference to the power requirements for the TAT undersea
cables requiring 7Kv feeds from each end (positive at one end, negative
at the other - a grand total of 14KV in all to power the repeaters which
AFAICR were spaced at 2Km intervals, extracting some 20 to 30 volts off
the line to power the repeaters which had been designed at the GPO (now
BT)'s research establishment (Dollis Hill, Martlesham) using the special
long life transistors that had also been developed there).

Unless I'm many miles out, I figured a total route length approximating
to some 4,800Km, implying a total of 2,400 undersea repeaters. Even
assuming 20v per repeater, a simple series arrangement would have
demanded a total supply voltage of 48Kv (24KV at each end, way higher
than the 7KV figure I recalled). Possibly the 20 or 30 volt drops were
shared between 3 repeaters at a time with the section of centre conductor
between each trio acting as a common bus bar supply.

In either case, such very long undersea cable routes would require power
feeding of the amplifiers (old analogue system) or regenerator/laser
amplifiers (today's modern optical fibre systems) where several kilovolts
are applied at each end of the power conductors (centre conductor of each
co-axial tube in the old analogue FDM days with the outer tube shield/
return acting as the ground return for the DC supply which neatly nulled
out any magnetic leakage which might attract the attentions of deep sea
sharks) so that each amplifier/regenerator could tap voltage off the
constant current supplied from each shore station.

Effectively, each repeater (or group of repeaters)'s power connections
are in series with each other rather like the heater strings in the early
valved (tubed) TV sets to minimise inefficiency in powering 6 to 12v (or
even higher?) 300mA valve heaters off a 120 or 240 volt mains supply in
the absence of an expensively screened and weighty mains transformer.

I should imagine that a modern undersea optical fibre cable would use an
outer screening conductor as the ground return for the DC power to effect
cancellation of magnetic field leakage. Whether this would rely on the
outer stainless steel armouring to supplement a copper tube screen ground
or simply as a ground return conductor in its own right, I couldn't say
but it's odds on that such a co-axial conductor power feeding arrangement
would be use whatever the technology of the repeaters simply to eliminate
any emanation of magnetic flux from the cable.

Although the use of good quality stainless steel in the armouring of
such under sea cables should eliminate distortions in the local magnetic
field, it's possible that the shark's electro senses may still be
detecting the cable's presence, especially in sections of the route where
the cable crosses trenches or depressions in the ocean floor's topology
where it will form a catenary suspension above the ocean floor to occupy
the space where sharks would be freely swimming and more likely to detect
the slightest of such anomalies. Sections of undersea cable lying on the
sea floor, perhaps sunk into mud or soft sand, will be largely screened
from such electro detection by sharks.

In view of the above, it's perhaps not surprising that the reporter
glossed over the complexities of modern undersea cables when describing
why sharks might have been attracted to the cable(s) and taking
exploratory nibbles out of this potential food source.


A 4800KM fiber might only need ten repeaters. But that won't change
the nature of the cable bundle, until the repeaters are
removed entirely. And that could happen. There are people
working on DSP techniques. I was unable to find
any practical (field) examples of that.

http://www.xtera.com/wp-content/uplo...2-May-2015.pdf

https://www.alcatel-lucent.com/press...nce-more-610km

Because it's a winner-take-all field, you're not likely
to find the very latest developments, until they're on a ship
out to sea.

Paul

En el artículo , Henry
Law escribió:

Every so often I see a really fascinating USENET post which reminds me
why I spend so much time on t'interweb. This was one of them; thank you.

Agreed. Thanks Johnny.

--
(\_/)
(='.'=) systemd: the Linux version of Windows 10
(")_(")

En el artículo l.net,
Dave Liquorice escribió:

They might be using light for that as well. I know it's been
researched and they could get a useable amount of power at the
reciving end.

Only small amounts, and very probably not enough for undersea repeaters.

Interesting research though.

https://share.sandia.gov/news/resour..._releases/pof/

--
(\_/)
(='.'=) systemd: the Linux version of Windows 10
(")_(")

On 02/07/2016 16:47, The Natural Philosopher wrote:
On 02/07/16 16:41, Fredxxx wrote:
On 02/07/2016 16:35, Mike Tomlinson wrote:

From the new dumbed-down Torygraph.

http://www.telegraph.co.uk/technolog...aunches-giant-
undersea-internet-cable/

"Although the optical fibres that transport data are extremely thin, the
cables have to be reinforced with layers of tubing, steel wires and
plastic to prevent damage. The cables have become a target for shark
attacks, with sharks possibly drawn to the electromagnetic signals
running through them"

Are you absolutely sure there aren't optical repeaters, in which case
currents might flow in the sheath?

I would still expect copper cables within the steel reinforcing to
supply the power.

There most definitely are repeaters, cos I worked on the design of one,
and yes, sharks do get attracted to the currents


Apart from which, surely the light travelling down the optical fibre
*is* an electromagnetic signal?

How it would get out is another matter.

On 03/07/2016 09:24, Paul wrote:

A 4800KM fiber might only need ten repeaters. But that won't change
the nature of the cable bundle, until the repeaters are removed
entirely. And that could happen. There are people working on DSP
techniques. I was unable to find any practical (field) examples of
that.

http://www.xtera.com/wp-content/uplo...2-May-2015.pdf



https://www.alcatel-lucent.com/press...nce-more-610km



Because it's a winner-take-all field, you're not likely to find the
very latest developments, until they're on a ship out to sea.

Paul

Soliton optical solutions may be the answer, they can use optical
amplifiers rather than repeaters.
There have been experiments with thousands of killometres of fibre AFAIK.

On 02/07/16 23:14, Johnny B Good wrote:
On longer, trans-oceanic routes measuring several thousand kilometres,
each end of the cable would be fed with an HT DC voltage measuring
several Kilovolts! (7KV at each end of the TAT cables being laid down in
the late 70s / early 80s afair - positive one end and negative the other
to provide a total of 14Kv over

That sounds about right. I worked* on P-TAT repeater software - shark
attack was a standing joke.

Fortunately it only affected shallow bits of cable



*or I would have done if anybody had been able to explain what they were
trying to do.

--
New Socialism consists essentially in being seen to have your heart in
the right place whilst your head is in the clouds and your hand is in
someone else's pocket.

On 03/07/16 01:05, Dave Liquorice wrote:
On Sun, 3 Jul 2016 09:35:18 +1000, Jacky Chance wrote:

The cables have become a target for shark attacks, with sharks
possibly
drawn to the electromagnetic signals running through them"

Um...

Pity about what powers the repeaters.

They might be using light for that as well. I know it's been
researched and they could get a useable amount of power at the
reciving end. Don't think it was very effcient though but things
could have improved.

Not with an 8086 involved.

The repeaters weren't just dumb amps,. They had the ability to switch
between fibres and IIRC report back on faults

And if there had been enough light power to power an amp, they wouldn't
have needed one! Doh!



--
The theory of Communism may be summed up in one sentence: Abolish all
private property.

Karl Marx

On 03/07/16 10:15, GB wrote:
On 02/07/2016 16:47, The Natural Philosopher wrote:
On 02/07/16 16:41, Fredxxx wrote:
On 02/07/2016 16:35, Mike Tomlinson wrote:

From the new dumbed-down Torygraph.

http://www.telegraph.co.uk/technolog...aunches-giant-

undersea-internet-cable/

"Although the optical fibres that transport data are extremely thin,
the
cables have to be reinforced with layers of tubing, steel wires and
plastic to prevent damage. The cables have become a target for shark
attacks, with sharks possibly drawn to the electromagnetic signals
running through them"

Are you absolutely sure there aren't optical repeaters, in which case
currents might flow in the sheath?

I would still expect copper cables within the steel reinforcing to
supply the power.

There most definitely are repeaters, cos I worked on the design of one,
and yes, sharks do get attracted to the currents


Apart from which, surely the light travelling down the optical fibre
*is* an electromagnetic signal?

How it would get out is another matter.


Its the magnetic field that the sharks detect IIRC.
You wont get a static magnetic field with light, and the whole point of
the fiber is to make sure it stay trapped inside




--
The theory of Communism may be summed up in one sentence: Abolish all
private property.

Karl Marx

On Sun, 03 Jul 2016 09:28:03 +0100, Mike Tomlinson wrote:

En el artÃ*culo , Henry
Law escribió:

Every so often I see a really fascinating USENET post which reminds me
why I spend so much time on t'interweb. This was one of them; thank
you.

Agreed. Thanks Johnny.

Well, thank you, Mike and Henry. These longer posts usually attract bric
bats (?) rather than accolades. :-)

I suppose the shorter than usual length of this post when I find myself
drawn into "Essay Mode" must have tempered the (in retrospect, often
understandable) urge to fling bric bats in my direction this time.

Damn it! Here I go again, turning a simple 'thank you' into a mini
essay! :-(

--
Johnny B Good

On 03/07/2016 12:48, Johnny B Good wrote:
On Sun, 03 Jul 2016 09:28:03 +0100, Mike Tomlinson wrote:

En el artÃ*culo , Henry
Law escribió:

Every so often I see a really fascinating USENET post which reminds me
why I spend so much time on t'interweb. This was one of them; thank
you.

Agreed. Thanks Johnny.

Well, thank you, Mike and Henry. These longer posts usually attract bric
bats (?) rather than accolades. :-)

I suppose the shorter than usual length of this post when I find myself
drawn into "Essay Mode" must have tempered the (in retrospect, often
understandable) urge to fling bric bats in my direction this time.

Damn it! Here I go again, turning a simple 'thank you' into a mini
essay! :-(

Being a fan of the "fuller" answer myself, I would add my thanks also ;-)


--
Cheers,

John.

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On 03/07/16 21:12, pamela wrote:
On 12:13 3 Jul 2016, The Natural Philosopher wrote:

On 02/07/16 23:14, Johnny B Good wrote:
On longer, trans-oceanic routes measuring several thousand
kilometres, each end of the cable would be fed with an HT DC
voltage measuring several Kilovolts! (7KV at each end of the
TAT cables being laid down in the late 70s / early 80s afair -
positive one end and negative the other to provide a total of
14Kv over

That sounds about right. I worked* on P-TAT repeater software -
shark attack was a standing joke.

Fortunately it only affected shallow bits of cable


*or I would have done if anybody had been able to explain what
they were trying to do.

You wrote you worked on P-TAT ...... and also that you would have
worked on P-TAT but didn't.

Which is it?

Well I spent 6 months bashing a keyboard, looking out of the window and
I even brought a telephoto to photo people in the park outside, but as
far as actually generating anything of use or value, I have no idea.

Since no one seemed to know what any of the program specifications meant.


A couple of blokes and I reckoned we could have written the whole thing
from scratch if we had thrown away the 'z notation' sacked the
management and RMX 86, written a lightweight multitasking kernel, and
hacked the thing together, in about 3 months

Instead it had about 35 programmers working on it.

And they still were when I left.

Money was OK tho.


--
Outside of a dog, a book is a man's best friend. Inside of a dog it's
too dark to read.

Groucho Marx