Hello,
Here i would like to add that we are using FSO because of high data rate , secure , fast link design in case of any disaster, cheap compared to all communication , ease of implementation , long distance etc.
long distance can be increased by laser beam (1550nm) with beam control ( which is not much tedious work ) ,turbulence mitigation technique like MIMO . OFDM . OAM , non- linear equalization technique etc.(need more).
AT 1550 nm , there is no much bad effect of weather condition as well as divergence no one can intercept it because we can apply encryption at quantum level. It is so much fast operation (with much wider bandwidth so that you can carry more user at time). If you want to deploy it anywhere else it doesn’t require licence of spectrum
Also it can cover thousand of million of KM like ( please visit inter-satellite communication at mars( upcoming).
I hope it will help.
Thanks