Résumé
The optical noise behavior of a 1.55 micrometer distributed feedback laser (DFB) has been investigated, in a medium frequency range (10 kHz-1 MHz). This noise characterization allows us to bring to the fore a high noise level due to mode competition. The presence of this process is also extremely notable on the analysis of the electrical noise, related to the laser voltage fluctuations. The tight link between both spectral densities, electrical and optical, is strengthened by the measurement of the correlation function. Finally, a theoretical study, based on rate equations, confirms the noise evolution in the absence of the feedback process.