An is a component with two or more ports that selectively transmits, redirects, or blocks an optical signal in a transmission medium. According to , an optical switch must be actuated to select or change between states. The actuating signal (also referred to as the control signal) is usually electrical, but in principle, could be optical or mechanical. (The control signal format may be Boolean and may be an independent signal; or, in the case of optical actuation, the control signal may.