Abstract : Mixing of two laser beams on a photo-detector is a way to generate radiofrequency signals up to THz band. By correlation of both optical sources, this signal can reach the required spectral purity for radio-over-fiber communications systems. Our work deals with the method of correlation by optical locking on a frequency comb. Injection locking is used to transfer the phase noise of a reference master laser to a slave laser. Using two harmonics line of a frequency modulated laser as two distinct master sources, the phase noises of both slave lasers are correlated and the frequencies difference become a multiple of the primary frequency. We have realized a general theoretical study of the injection into semi-conductor laser with complex cavity, in particular distributed feedback lasers, showing in particular the geometrical asymmetry of the noise properties. The correlation degree between the lasers has been analytically linked to the injection parameters and the phase noise characteristics. Measurements concerning interferences fringes contrast and heterodyne photocurrent spectrum have confirmed the expression. The temporal beating phenomenon has been compared with Fourier optics and speckle. Spectral purity of the beat-note has been studied and fundamental limits of this technique derived in function of the quality of the primary oscillator, the spectral proprieties of the lasers, the parameters of injection and fiber transportation. Phase noise measurements on the experimentally generated radio-frequency signal, for different conditions of injection, are in good agreement with analytical expressions.