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People laid undersea cables for telegraphs and back then it was a big deal. However, it's been 154 years and people stopped being impressed a while ago. http:/

People laid undersea cables for telegraphs and back then it was a big deal. However, it's been 154 years and people stopped being impressed a while ago. http://en.wikipedia.org/wiki/Transatlantic_telegraph_cable http://en.wikipedia.org/wiki/Transatlantic_telegraph_cable

sausagefeet 15y ago
It's so weird because I think it's such an impressive feat and one of those things that I feel should be technically really challenging yet it was done so long ago. Sometimes I learn things and am shocked because I either thought accomplishing the thing would be easy and it turns out to be insanely hard or vice versa. This is the latter.
saulrh 15y ago
Modern telecoms cable is some amazing stuff. These days there's no metal in the entire cable. Instead, it's all lasers through glass fiber, and when the signal attenuates, it gets boosted by passing through sections of doped fiber that lase using power from another beam, adding power to the signal. And we can do this just as easily as the people back then dropped telegraph cable. For me, at least, there's always something to be impressed by.
- Nrsolis 15y ago
  That's not strictly true. First, most EDFA (Erbium Doped Fiber Amplifiers) need power to operate since the lasers that perform the pumping action are local to the doped sections of fiber. Second, most submarine cables make extensive use of Raman amplification which leverages the transmission fiber as a gain medium via forward or backward pumping of lasers with frequencies chosen to produce Raman gain. In both cases, you need an amplifier every 70-100km (150km in some cases) in order to have a usable signal on a long span.
  - saulrh 15y ago
    Huh, didn't know that. I stand corrected. That Raman amplification is nifty. :D
    - Nrsolis 15y ago
      Raman amps are pretty cool but tricky. For one thing, the power required is pretty high. +1W dBm isn't uncommon for certain Raman amps. At those power levels, you need to be careful you dont cause burns to personel when they are working on the equipment. The power to run the lasers is usually carried on conductors that are part of the cable itself. The voltages are somewhere in the several kilovolt range so laying submarine cable is also kinda like laying a high-volage transmission line across the ocean.

sausagefeet 15y ago

It's so weird because I think it's such an impressive feat and one of those things that I feel should be technically really challenging yet it was done so long ago. Sometimes I learn things and am shocked because I either thought accomplishing the thing would be easy and it turns out to be insanely hard or vice versa. This is the latter.

saulrh 15y ago

Modern telecoms cable is some amazing stuff. These days there's no metal in the entire cable. Instead, it's all lasers through glass fiber, and when the signal attenuates, it gets boosted by passing through sections of doped fiber that lase using power from another beam, adding power to the signal. And we can do this just as easily as the people back then dropped telegraph cable. For me, at least, there's always something to be impressed by.

Nrsolis 15y ago
That's not strictly true. First, most EDFA (Erbium Doped Fiber Amplifiers) need power to operate since the lasers that perform the pumping action are local to the doped sections of fiber. Second, most submarine cables make extensive use of Raman amplification which leverages the transmission fiber as a gain medium via forward or backward pumping of lasers with frequencies chosen to produce Raman gain. In both cases, you need an amplifier every 70-100km (150km in some cases) in order to have a usable signal on a long span.
- saulrh 15y ago
  Huh, didn't know that. I stand corrected. That Raman amplification is nifty. :D
  - Nrsolis 15y ago
    Raman amps are pretty cool but tricky. For one thing, the power required is pretty high. +1W dBm isn't uncommon for certain Raman amps. At those power levels, you need to be careful you dont cause burns to personel when they are working on the equipment. The power to run the lasers is usually carried on conductors that are part of the cable itself. The voltages are somewhere in the several kilovolt range so laying submarine cable is also kinda like laying a high-volage transmission line across the ocean.