Patent ID: 7400793

Claim:
An apparatus comprising: a first optical device receiving a first wavelength division multiplexed (WDM) light, comprising a substrate, a slab waveguide formed on the substrate, and channel waveguides of differing lengths formed on the substrate, wherein the first WDM light is input to the slab waveguide to thereby travel through the slab waveguide and be input to the channel waveguides of differing lengths, the channel waveguides of differing lengths having differences in optical path lengths, respectively, so that lights at different wavelengths in the first WDM light are angularly dispersed from an end face of the substrate in different directions, respectively, in accordance with wavelength; a second optical device receiving a second WDM light, comprising a substrate, a slab waveguide formed on the substrate, and channel waveguides of differing lengths formed on the substrate, wherein the second WDM light is input to the slab waveguide to thereby travel through the slab waveguide and be input to the channel waveguides of differing lengths, the channel waveguides of differing lengths having differences in optical path lengths, respectively, so that lights at different wavelengths in the second WDM light are angularly dispersed from an end face of the substrate in different directions, respectively, in accordance with wavelength; at least one focusing device focusing the lights at different wavelengths angularly dispersed from the first optical device at different positions, respectively, and focusing the lights at different wavelengths angularly dispersed from the second optical device at different positions, respectively, so that angularly dispersed light from the first optical device and angularly dispersed light from the second optical device at the same wavelength are focused at the same position; and a reflector positioned at said same position and controllable so that a reflection angle of the reflector is adjusted to cause the light from the first optical device to be either returned to the first optical device or reflected to the second optical device.