  Controlled transitions between a hierarchy of n-scroll attractors are
investigated in a nonlinear optoelectronic oscillator. Using the system's
feedback strength as a control parameter, it is shown experimentally the
transition from Van der Pol-like attractors to 6-scroll, but in general, this
scheme can produce an arbitrary number of scrolls. The complexity of every
state is characterized by Lyapunov exponents and autocorrelation coefficients.
