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 <patr...@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 > patr...@zill.net > >
