Re: If that's really true
Edit: Bugger!!! - Jock beat me to it while I was trying to write a comprehensive answer :)
Regeneration an amplification are different - amplification is an analogue process, and, just like audio amps, optical amps introduce noise, distortion, etc each time the signal is amplified. Amplification occurs in the aggregated optical domain and the amplifiers, being an analogue device, are signal rate and content agnostic. I've worked with systems where there were different signal rates being carried by different wavelengths. An amplifier has no access to the signal content and can't even read the optical transport section overhead data - at this level the data stream for managing the amplifiers is carried on a separate wavelength that is dropped and inserted at each amplifier site.
Regeneration is a process in which the analogue optical signal is demodulated, optical transport section overheads removed, the individual wavelength payloads extracted, regenerator section overheads removed, re-shaped, re-timed, repackaged (new regenerator section overheads wrapped around payload) and then goes through the process to be sent on as an aggregate analogue optical signal again. Regeneration happens in the electrical domain and as a result regenerators must be designed for the specific signal rate and protocol they are regenerating.
Regenerator spacing is determined by how far can you go and how many times can the signal be amplified and still extract useful information at the end of it - this is largely determined by the modulation method chosen and the ability of your chosen forward error correction mechanism to recover errors.
Amplifiers are generally spaced at around 60~80km, depending on the system design, especially in terrestrial systems where if possible you want to put them in sites you already own. Submarine cable power feed voltages are determined by the number of amplifiers equipped - each one needs 50V at around 2.5 amps. I have seen systems that feed around +25kV for one end and -25kV from the other, for a total voltage drop of around 50kV end to end.
I've been out of the industry for about 3 years now, so some of this may be slightly dated.