When fitter, I really enjoyed experimenting with this. Actually, I don't think this needs a licence at all, but it is real experimentation. Anyone can do this without costing much.
All my gear and much of my test gear was homemade and very inexpensive. It is real "back of the garage" stuff. All my gear was homemade in the back of the garage. The only special test gear was a very weakly lit LED. If you have a multi-meter and scope, you really don't need much else. In my view optical communications is easier than microwaves as the test equipment is easy.
I was quite surprised how easy it was to copy an optical signal "over the horizon".
See https://sites.google.com/view/g3xbm4/home/optical-nanowaves/over-the-horizon .