A New TransAtlantic Cable System

Dorn Hetzel dhetzel at gmail.com
Mon Oct 4 22:22:58 UTC 2010


With regards to the Wired Article, I still have my copy of that issue and
would consider that article perhaps my favorite magazine article of all
time.

On Mon, Oct 4, 2010 at 1:41 PM, Patrick Giagnocavo <patrick at zill.net> wrote:

> On 10/4/2010 1:24 PM, Heath Jones wrote:
> >> By the way, my recollection is the undersea regenerators do purely
> optical regeneration.
> >> There is no O-E conversions undersea, only at the landing stations and
> terrestrial components.
> >
> > I'm not clever enough to know of some way that you could do optical
> > regeneration without converting the signal to electrical and
> > retransmitting back as optical.. How is that done?
> >
> >
>
> A halfway-decent description of the physics of how this is done, is
> covered in Neal Stephenson's excellent article on Wired:
>
> http://www.wired.com/wired/archive/4.12/ffglass.html
>
> The specific page covering optical regeneration:
>
> http://www.wired.com/wired/archive/4.12/ffglass.html?pg=6&topic=
>
> quote:
>
> ====
> These signals begin to fade after they have traveled a certain distance,
> so it's necessary to build amplifiers into the cable every so often. In
> the case of FLAG, the spacing of these amplifiers ranges from 45 to 85
> kilometers. They work on a strikingly simple and elegant principle. Each
> amplifier contains an approximately 10-meter-long piece of special fiber
> that has been doped with erbium ions, making it capable of functioning
> as a laser medium. A separate semiconductor laser built into the
> amplifier generates powerful light at 1,480 nm - close to the same
> frequency as the signal beam, but not close enough to interfere with it.
> This light, directed into the doped fiber, pumps the electrons orbiting
> around those erbium ions up to a higher energy level.
>
> The signal coming down the FLAG cable passes through the doped fiber and
> causes it to lase, i.e., the excited electrons drop back down to a lower
> energy level, emitting light that is coherent with the incoming signal -
> which is to say that it is an exact copy of the incoming signal, except
> more powerful.
>
> ====
>
> Cordially
>
> Patrick Giagnocavo
> patrick at zill.net
>
>



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