The authors demonstrate the optical generation of self-pulsations in c
omplex-coupled DFB laser diodes by selectively positioning the facet w
ith respect to the internal grating. The self-pulsations are accompani
ed by a strong intensity noise enhancement which partly originates fro
m mode competition. Applying a simple model they determine the imagina
ry part of the complex coupling coefficient from the self-pulsation fr
equency.