Abstract: An optical attenuator includes a first multi-mode waveguide varying a phase of an optical signal input through an input terminal; first and second single-mode waveguides having an input terminal coupled to an output terminal of the first multi-mode waveguide and varying a phase of the optical signal by a thermo-optic effect by electrodes attached thereto; and a second multi-mode waveguide having an input terminal coupled to an output terminal of the first and second single-mode waveguides and varying a phase of the optical signal, wherein a predetermined optical power distribution obtained by offsetting or adding up a phase varied in the first and second multi-mode waveguides and a phase varied by the thermo-optic effect is transferred to an output terminal of the second multi-mode waveguide.

Abstract: An optical waveguide filter including a multi-mode waveguide having a predetermined width, a predetermined length and a predetermined thickness includes a transmitting light source and a photo detector coupled to one side of the multi-mode waveguide; and a transmission line coupled to the other side of the multi-mode waveguide, wherein one hundred percent of an output optical power having a first wavelength from the transmitting light source is transferred to the transmission line, and one hundred percent of an input optical power having a second wavelength from the transmission line is transferred to the photo detector.

Abstract: An optical waveguide filter including a multi-mode waveguide having a predetermined width, a predetermined length and a predetermined thickness includes a transmitting light source and a photo detector coupled to one side of the multi-mode waveguide; and a transmission line coupled to the other side of the multi-mode waveguide, wherein one hundred percent of an output optical power having a first wavelength from the transmitting light source is transferred to the transmission line, and one hundred percent of an input optical power having a second wavelength from the transmission line is transferred to the photo detector.

Abstract: An optical attenuator includes a first multi-mode waveguide varying a phase of an optical signal input through an input terminal; first and second single-mode waveguides having an input terminal coupled to an output terminal of the first multi-mode waveguide and varying a phase of the optical signal by a thermo-optic effect by electrodes attached thereto; and a second multi-mode waveguide having an input terminal coupled to an output terminal of the first and second single-mode waveguides and varying a phase of the optical signal, wherein a predetermined optical power distribution obtained by offsetting or adding up a phase varied in the first and second multi-mode waveguides and a phase varied by the thermo-optic effect is transferred to an output terminal of the second multi-mode waveguide.