TIME-SHARING WAVELENGTH MONITORING APPARATUS

PROBLEM TO BE SOLVED: To obtain a time-sharing wavelength monitoring apparatus which reduces a cross talk even when a wavelength multiplexing number is increased and by which respective wavelengths can be measured with high accuracy by a method wherein wavelength multiplexing light is demultiplexed, one arbitrary wavelength is selected by an optical gate switch and a cross wavelength is discriminated. SOLUTION: Wavelength multiplexing light in which a plurality of beams of wavelength light λ1 to λn are multiplexed is input to a prescribed input port in an array waveguide diffraction grating 21, and it is demultiplexed so as to be input to a plurality of optical gate switches 22 from prescribed output ports. The optical gate switches 22 are ON-OFF-controlled individually by a switch control circuit 23, and only wavelength light from one object to be monitored is output. In an array waveguide diffraction grating 11, respective beams of wavelength light which are input individually to corresponding input ports are output from adjacent prescribed output ports #j, #j+1, and they are discriminated by a photodetector and a computing means (a logarithmic amplifier) so as to be output as wavelength monitoring outputs. Wavelength monitoring outputs (error outputs) with reference to reference wavelength light λref which are output from output ports #k, #k+1 are fed back to a temperature control circuit via a negative feedback loop.