Big customers are researchers and developers in optical communications, where you have signals that go to these bandwidths. Also microwave engineers working on

Big customers are researchers and developers in optical communications, where you have signals that go to these bandwidths. Also microwave engineers working on next generation wireless systems, as well as people working in THz communications. Those are the ones I know about, I'm sure there are many customers in defence/security but I have no idea about those applications.