Analytical analysis of IF-penalties for different FSK and CPFSK detection schemes

Due to the nonnegligible laser linewidth in coherent optical systems, IF bandwidths larger than the Nyquist signaling rate are required. This causes additional sensitivity penalties, which are evaluated for three types of coherent optical FSK (frequency-shift-keying) detection; two-filter-, delay-line discriminator-, and phase-diversity detection. Sensitivity as a function of the relative IF-bandwidth is given in a fully analytical form and confirmed by experimental measurements.<
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