A free space optical switch that uses both an open loop control mode and a
closed loop control mode. The open loop control mode is used to
transition to a state where at least some light is sensed at a
destination port. A closed loop control mode is then used, whereby a
series of controlled dither signals are adjusted for system dynamics.
Modifying the dither signals in this matter allows moving actuators at a
rate that is much closer to the natural frequency of the underlying
system, and hence speeds up the system convergence process. Variable
modulation amplitudes may be employed on the dither signals to maximize
convergence speed. In particular, changes in the dither signal can be
made in accordance with the change in amplitude as a function of a
gradient along a parabola that models the optical system response.
According to still further aspects, the dither signals may be compensated
for a desired and selectable attenuation level of output optical power.