[frankjr]

> undersea fiber-optic cables is that they need amplifiers every N kilometers

Huh, I had no idea it needs to be done so frequently.

> These days optical cable repeaters are photon amplifiers that operate at full gain at the bottom of the ocean for an anticipated service life of 25 years.

> Repeaters are a significant cost component of the total cable cost, and there is a compromise between a ‘close’ spacing of repeaters, every 60km or so, or stretching the inter-repeater distance to 100km and making significant savings in the number of repeaters in the system. On balance it is the case that the more you are prepared to spend on the cable system the higher the cable carrying capacity.

https://blog.apnic.net/2020/02/12/at-the-bottom-of-the-sea-a...

https://www.rp-photonics.com/propagation_losses.html

https://www.rp-photonics.com/fiber_amplifiers.html