Patent ID: 7469079

Claim:
A broadband wavelength multiplexing and demultiplexing filter comprising: Mach-Zehnder optical interferometer circuits each having directional couplers formed on a substrate by a first optical waveguide and a second waveguide provided in parallel to each other with a gap in a lengthwise direction of the optical waveguides therebetween, and a phase part interposed between the directional couplers; a first point-symmetrically connected optical interferometer circuit formed by accurately point-symmetrically connecting two equal Mach-Zehnder optical interferometer circuits in series; and a light input side circuit formed by connecting one or more first point-symmetrically connected optical interferometer circuits in series; wherein a light input terminal of a first optical waveguide of the light input side circuit is composed of an input port for optical signals having a plurality of wavelengths, and an output terminal of the first optical waveguide is composed of a through port, an output terminal of a second optical waveguide of the light input side circuit is composed of a cross port, a first light output side circuit formed by serially connecting one or more second point-symmetrically connected optical interferometer circuits having the same functional structure as the first point-symmetrically connected optical interferometer circuit is connected to the through port, and a second light output side circuit including one or more Mach-Zehnder optical interferometer circuits having transmission characteristics different from those of the Mach-Zehnder optical interferometer circuits constituting the first and the second point-symmetrically connected optical interferometer circuits is connected to the cross port.