A dispersion compensating fiber exhibiting low losses is used to study the phase to amplitude noise and amplitude to phase noiseconversion mechanisms with a very good signal-to-noise ratio over a 20 GHz bandwidth. It is shown that the large frequency noise ofsemiconductor lasers and the losses in the fiber restrain this technique from efficiently reducing the relative intensity noise to improvethe dynamic range of opto-microwave links. However, these properties are proved to be useful to precisely characterize the laser phase noiseover a large bandwidth.