DYNAMIC-RANGE OF EXTERNALLY MODULATED ANALOG OPTICAL LINKS - OPTICAL AMPLIFICATION VERSUS COHERENT DETECTION

Two externally modulated analog optical links (a direct detection link using an optical preamplifier and a coherent AM link) are analyzed an d compared with the conventional direct detection link. For received o ptical power less than 1 mW, the optical preamplified link and the coh erent AM link have a better performance than the direct detection link . However, the coherent AM link is more susceptible to relative intens ity noise (RIN) than the direct detection links (both amplified and un amplified) and have a RIN-limited spurious-free dynamic range (SFDR) o f 4 dB less than that of the direct detection links. Therefore, optica lly preamplified direct detection links may be more attractive in impr oving the SFDR of analog systems.