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Comment Re:how do they do it today? (Score 1) 59

The receive sensitivity on common '10G' DWDM optics is frequently down to -24 dBm or lower. That's less than a hundredth of a mw. So from that perspective, that +0 or +3 dBm is rocket hot. 100G optics aren't quite as sensitive, but still down to -14 or -17 or so depending on the specs.

Comment Re:how do they do it today? (Score 3, Informative) 59

This sort of thing is measured in dBm to make the math easier. Decibel Milliwatts, where 0 dBm = 1 mw and it's a logarithmic scale up and down from there.
Individual channels are on the order of 0 to 5 dBm, or 1 to 3 mw. The composite signal coming out of an amplifier, which consists of multiple channels, is on the order of 20 dBm depending on how many channels are active and what the reach of the amplifier is. That's about 100 mw. Definitely a laser safety concern, but not military style death ray.

Comment Re:how do they do it today? (Score 1) 59

There are, which is why the electricity is at very high voltages to overcome it, which is why it attracts sharks. I'm more of a terrestrial guy, but if i remember correctly what they do is apply a very high + voltage on one end of the cable and a very high - voltage on the other end, and the amplifiers are powered in series inside of 'festoons' on the bottom of the ocean.

Comment Re:how do they do it today? (Score 4, Informative) 59

But there are still going to be amplifiers. They are referring to eliminating transponders, which we already don't use for modern sub-sea links. This is basically just 16QAM, but instead of using 4 symbols over 1 frequency, it's 2 symbols over 2 frequencies tightly spaced together. It's been understood for a while that widening the channels was probably the only way to go beyond 100gbps for a transmitter/receiver.

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