"pamela" wrote in message
...
On 21:39 3 Jul 2016, The Natural Philosopher wrote:

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.

You wrote, "I even brought a telephoto to photo people in the park
outside". Well that's seems unusual!

Depends on what those people were doing in the park.

dennis@home wrote:
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.

In the Real World, things are decidedly utilitarian.
There are a *lot* of repeaters on this one. I guess like
most things in life, the emphasis is on quantity over
quality. And this cable only cost $300 million. It's a
mere 2cm in diameter (and is buried). Not a lot of
diameter for reinforcement. So a shark who wants to
bite this one, will have to catch the cable as
it goes over some "bumps".

http://www.pcworld.com/article/29479...sea-cable.html

And this describes a state-of-the-art coherent detection (DSP)
method at 100Gbit/sec. The repeater distance is consistent with
the info in the previous article.

https://www.ntt-review.jp/archive/nt...201108fa2.html

And I get a third (mis-stated) total bandwidth figure in
this video. I think in journalism school they emphasize
"just put in some numbers and let God sort it out".
Maybe the total cable is rated 60Tbit/sec (6 pair times
100Gbit/sec times 100 wavelengths) ? I can see a power
converter in the middle of the unit, but cannot
recognize much more of what is in there. The interesting bit
isn't in the transparent section. The repeater looks kinda
small for digital repeatering, so maybe an optical
technique is used.

http://www.computerworld.com/video/4...-across-oceans

Apparently there are 6 fiber pairs in the cable, and for
its part in the investment, Google gets one pair for their
own usage (so they bought a sixth of the cable).

And that thing was supposed to be turned on, a couple
days ago. (Now they have to call tech support, turn
it off and on again, set their browser to 192.168.1.100
and so on.)

Paul