4 ms·
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
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 agoHuh, didn't know that. I stand corrected. That Raman amplification is nifty. :D
- Nrsolis 15y agoRaman 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.