  The chaotic dynamics of directly modulated semiconductor lasers with delayed
optoelectronic feedback is studied numerically. The effects of positive and
negative delayed optoelectronic feedback in producing chaotic outputs from such
lasers with nonlinear gain reduction in its optimum value range is investigated
using bifurcation diagrams. The results are confirmed by calculating the
Lyapunov exponents. A negative delayed optoelectronic feedback configuration is
found to be more effective in inducing chaotic dynamics to such systems with
nonlinear gain reduction factor in the practical value range.
