Résumé
Medium frequency (100 kHz 1 MHz) measurements of electrical noise power spectrum density in DBR tunable lasers show particular behavior around threshold, compared to classical edge-emitting structures. In this paper, we consider structures in which tunability is made by current injection. Standard monomode (SMSR greater than 40 DB) non tunable DBR lasers Noise Level follow a global shot- noise tendancy, except around the laser threshold current level (called Ith). In these structures, a strong excess of noise is classically established at Ith. Next, at Ith+epsilon, the noise level goes down again to the shot noise level. In DBR tunable lasers, this behavior is exactly the same, except that epsilon grows up when the current level in the Bragg section gets stronger. The aim of this paper is to establish a link between the 'epsilon' factor and the current level in the Bragg section.