Abstract-Measurements of relative intensity noise and modulation response, before and after propagation in optical fiber, of the output field of multiquantum-well distributed-feedback (MQW-DFB) lasers are used to determine the influence of the intraband damping mechanisms, the DFB structure and the carrier transport and carrier capture into the QW's on the laser chirp. The power dependence of the linewidth enhancement factor is shown to explain the saturation of the laser linewidth at high optical powers.