This paper presents experimental and numerical results on the effects of both intra and extra-cavity dispersion on a coupled opto-electronic oscillator (COEO) phase noise and its deterministic behavior. The combined effects of the optical intracavity dispersion and the detuning of the two oscillating loops strongly affects the COEO quality factor and its phase noise spectrum. The observed phase noise changes are correlated to the deterministic optical pulse shape, which turns out to be a simple parameter for noise optimization. The oscillation stability is also considered and particularly its dependence on the extra-cavity fiber spool dispersion. Finally, the dispersion management of a COEO can be completed by adjusting the Mach-Zehnder Modulator (MZM) bias voltage. By applying the proposed method, a phase noise performance below-120 dBc/Hz at 1 kHz offset from 10 GHz has been obtained.