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 and compared with the conventional direct detection link. For received optical power less than 1 mW, the optical preamplified link and the coherent AM link have a better performance than the direct detection link. However, the coherent AM link is more susceptible to relative intensity noise (RIN) than the direct detection links (both amplified and unamplified) and have a RIN-limited spurious-free dynamic range (SFDR) of 4 dB less than that of the direct detection links. Therefore, optically preamplified direct detection links may be more attractive in improving the SFDR of analog systems.<
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