Optical and mm-wave links face-off for the future

The advantages of optical systems are compared with those of millimeter-wave systems, noting that the latter are more susceptible to electromagnetic interference. A comparison is also made between the transmitter candidates for millimeter-wave links: the traveling-wave tube and the IMPATT diode. It is noted that in a millimeter-wave system, various types of RF amplitude modulation can be achieved by using the nonlinear properties of diodes and transistors. Frequency and phase modulation require frequency dispersive or phase-delay elements together with the nonlinear devices. In comparisons between fiber-optic and millimeter-wave guided systems for terrestrial applications, the fiber-optic system exhibits significant advantages for transmitter-receiver distances exceeding 75 ft.