Richard Steenbergen has regularly given the presentation "Everything You Always Wanted to Know About Optical" at NANOG over the years; October 2019:

* https://www.youtube.com/watch?v=nKeZaNwPKPo

APNIC/NZNOG had a good presentation focusing on sub-sea optical stuff (January 2020)):

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

For longer distances (>100km), you want to do a search for "coherent optics".