Abstract
It is shown that drive current noise could lead to an important increase of linewidth and a Gaussian line shape of tunable multielectrode distributed Bragg reflector (DBR) lasers. As an example, the drive current noise induced linewidth (DCNIL) has been measured to be about 120 MHz using a standard DC source through at 50 Omega resistor to drive the Bragg section of a tested DBR laser. For tunable lasers with an electronic tuning efficiency of more than 1 GHz/mA ultralow noise current sources should be used to ensure a negligible DCNIL.