Wavelength selective optical switch

A wavelength selective optical switch which includes optical path switching means provided with a plurality of mirrors on which signal lights of respective wavelengths contained in a wavelength division multiplexed light are incident, for controlling angular variable reflecting surfaces of said respective mirrors to switch optical paths for the signal lights reflected by said respective mirrors to arbitrary directions for each wavelength, comprising:

• wavelength detecting means for detecting the wavelengths of the signal lights input to said optical path switching means;
• monitor light generating means for generating a monitor light for monitoring and controlling the reflecting surface angles of said plurality of mirrors, irrespectively of the wavelengths of the signal lights input to said optical path switching means;
• a monitor light input port to which the monitor light from said monitor light generating means is input;
• a monitor light output port to which the monitor light emitted from said monitor light input port and reflected by said respective mirrors of said optical path switching means is coupled;
• monitor light intensity detecting means for detecting the intensity of the monitor light output from said monitor light output port;
• and
• control means for feedback controlling, for the wavelength of the signal light capable of being contained in the wavelength division multiplexed light, which is not input to said optical path switching means, the reflecting surface angle of the corresponding mirror in said optical path switching means based on detection results of said wavelength detecting means and said monitor light intensity detecting means, so that the intensity of the monitor light output from said monitor light output port becomes maximum.