We investigate, theoretically and experimentally, three analog optical links: (a) a direct detection link with an optical preamplifier, (b) a coherent AM (Amplitude-Modulated) link and (c) a coherent AM link with an optical preamplifier, and compare their performance with a conventional direct detection link. The theoretical analyses and the experimental measurements present cross-over points between the four links' dynamic range performance, and agree that these are due to certain noise terms like thermal noise, shot noise, relative intensity noise (RIN), signal-ASE (amplified spontaneous emission) beat noise, ASE-ASE beat noise, and LO (local oscillator) -ASE beat noise becoming dominant as the received optical power changes. For low received optical power, the use of an optical amplifier, coherent detection and the combination of both techniques can be used to improve the dynamic range over the conventional direct detection link. However, in the shot noise-limited regime, the conventional direct detection link gives the best performance. We also show that coherent AM links are more sensitive to RIN than the direct detection links. The RIN-limited spurious-free dynamic range of the coherent AM links is 4 dB worse than that of the direct detection links.