Optical gate device, manufacturing method for the device, and system including the device

A system comprising:

• an optical gate device comprising a first optical coupler including first and second optical paths directionally coupled to each other, a nonlinear optical medium for forming a loop optical path connecting said first and second optical paths, and a second optical coupler including a third optical path directionally coupled to said loop optical path;
• a probe light source connected to said first optical path for supplying probe light to said first optical path;
• a first optical fiber transmission line connected to said third optical path for supplying an optical signal to said third optical path;
• and
• a second optical fiber transmission line connected to said second optical path for transmitting a converted optical signal output from said second optical path, wherein said optical signal is a wavelength division multiplexed signal whose channels are shifted from each other along a time axis, whereby said converted optical signal becomes a time division multiplexed signal having wavelengths equal to the wavelength of said probe light.