Interferometric noise of RF phase-modulated noisy light

In this paper, we propose and demonstrate a new and original model for theoretical calculation of the noise power spectral density (NPSD) in phase-modulated optical links. The phase modulation is operated in the RF frequency range by an external phase modulator. The NPSD is derived for the first time in interferometric systems, by considering all effects such as the 1/f FM noise of the laser, and white noise applied to light from a 1550 nm DFB laser, with phase modulation. The results show for the first time the influence of the phase modulation index, modulation frequency, and interferometric delay in the phase-to-intensity noise conversion. Theoretical calculations and experimental results of conversion of FM-noise to intensity noise in an optical link are shown with good agreement.