[nine_k]

Fair! And the existing MW re-translator towers can be upgraded / reused this way.

Lasers have a downside though: optical and near IR light is much more readily absorbed by water vapor than microwaves. I wonder if a maser would be an acceptable solution, if cheaper versions of it existed.

[looofooo]

1550nm water is super transparent.

[adrian_b]

Not at all.

While 1550 nm falls between two absorption maxima of water, so it is not the worst choice, the absorption in water is still more than one hundred times higher than at e.g. 905 nm.

Because of this, 1550 nm is absorbed through fog or clouds at least 3 to 5 times more than shorter wavelengths like 905 nm. Even the latter is absorbed a lot by water, while being much more dangerous for eyes than 1550 nm.

There is no near infrared wavelength where the water absorption is negligible.

See the graphs at:

https://en.wikipedia.org/wiki/Electromagnetic_absorption_by_...