Optical signal processing circuit

An optical gate switch circuit comprising:

• an asymmetric Mach-Zehnder interferometer having an optical path that outputs control light and probe light to a second optical directional coupler via a first optical directional coupler and an optical phase modulation element, and another optical path that connects a third optical directional coupler to which the probe light is input, to the second optical directional coupler via a variable optical attenuator and an optical phase shifter;
• and
• a bandpass filter connected to the second optical directional coupler;
• wherein the intensity modulated control light with a wavelength of λC is input to the optical phase modulation element, the probe light with a wavelength of λP being clock signal light or continuous light is input to the asymmetric Mach-Zehnder interferometer, the probe light outputted from the asymmetric Mach-Zehnder interferometer is extracted through the optical bandpass filter, and thereby switching of the probe light outputted from the optical bandpass filter is performed in response to the control light.