In controlling an optical switch that includes an incoming light
deflection section to deflect incoming light from a predetermined input
port in an arbitrary direction, and an outgoing light deflection section
to deflect outgoing light from the incoming light deflection section in
an arbitrary direction and couple the outgoing light to a predetermined
output port, a monitoring section monitors optical coupling efficiency of
the outgoing light into the output port and controller controls
deflection characteristics of the deflection sections so that the
monitored optical coupling efficiency is maximized. Therefore, even when
optimal controlled variables for the optical switch are displaced due to
temperature drift and/or drift over time, the time taken to find the
optimal controlled variables can be significantly reduced and rapid
switching of optical paths can be achieved.