We characterize the chaotic dynamics of semiconductor lasers subject
to either optical or electro-optical feedback modeled by Lang-Kobayashi and
Ikeda equations, respectively. This characterization is relevant for secure
optical communications based on chaos encryption. In particular, for each
system we compute as a function of tunable parameters the Lyapunov spectrum,
Kaplan-Yorke dimension and Kolmogorov-Sinai entropy.