How is the modulation technique used?

What are the modulation technique for microwave communication? is the same technique used 4 free space optics?

• i want to know what modulation techniques used for microwave terestrial communicton and wireless optical communication?

• Answer:

  FM and AM are usually used for lower frequencies (1 to 200 megahertz, roughly) Pulse modulation is rare. I've never seen it used except in text books. Frequency shift key is common in higher bands from UHF to SHF (300 to 4000 megahertz). It accomodates digital signals more easily than the others.