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Optical Heterodyne Limiter-discriminator and Discriminator FSK Systems

We present a rigorous model for heterodyne FSK systems with limiter-discriminator as well as with discriminator detection. The system performance is impaired by receiver noise as well as laser phase noise. A best sensitivity for the limiter discriminator system is 39.9 generated photo electrons for a 10 −9 bit error-rate whereas for the discriminator system it is 49.2 photo electrons. The system performances are compared to that of ASK and dual filter FSK systems. It is found that significant amounts of phase noise can be tolerated for all the systems provided that sufficient IF bandwidth is allocated and a large modulation index value is used (for the FSK systems)