Microwave fiber-optic communications systems

Various microwave fiber-optic (FO) system applications, including electronic countermeasures (ECM), radar signal processing, antenna/radio remoting, sensor arrays, multichannel video transmission, etc., are described. Laser diode (LD) nonlinearity and noise, as well as system design criteria, are discussed. With efficient techniques of nonlinearity compensation and LD noise reduction, the microwave FO system can achieve low distortions and sufficient signal-to-noise ratio (S/N) for high quality signal transmission. Both 0.8-0.9 and 1.1-1.6 micron LD and photodetector selection and characterization are presented for microwave FO design. Special attention is given to the metal semiconductor field-effect transistor (MESFET) which, as a photodetector, provides advantages of low noise and low bias voltage. Also, the MESFET is an excellent device as a microwave LD driver and low noise postdetector amplifier. Consequently, monolithic microwave FO integrated circuits are possible. A wideband FO link is given as an example of the optoelectronic circuit design procedure.