Our paper is devoted to a new type of the precision RF oscillator—the so-called optoelectronic oscillator (OEO). The OEO can be used as the RF oscillator and as the correlator of random variables (signals). The laser modulation modes in OEO are studied, taking into account the problem of the carrier frequency suppression. It is shown that the spectral power density of the phase noise power of OEO depends on the laser phase noise, laser coherence time, the choice of modulation modes, the level of the DC component suppression, the degree of alignment of lateral optical harmonics during modulation, the equality of excitation coefficients of optical channels in the Mach–Zehnder modulator, the geometric length of the optical fiber, and the optical power.