Abstract: An optical transmitter includes an electro-optic modulator, a monitor circuit that monitors output light of the electro-optic modulator, and a processor that controls a bias voltage of the electro-optic modulator using a monitoring result of the monitor circuit, wherein the processor superimposes a first dither signal with a first frequency and a second dither signal with a second frequency different from the first frequency, onto one bias voltage in a time sharing manner, calculates a first control error based on a first component oscillating at the first frequency and a second control error based on a second component oscillating at the second frequency based on the monitoring result, and determines a control value for controlling the bias voltage using the first control error and the second control error.

Abstract: An optical transmitter includes an electro-optic modulator, a monitor circuit that monitors output light of the electro-optic modulator, and a processor that controls a bias voltage of the electro-optic modulator using a monitoring result of the monitor circuit, wherein the processor superimposes a first dither signal with a first frequency and a second dither signal with a second frequency different from the first frequency, onto one bias voltage in a time sharing manner, calculates a first control error based on a first component oscillating at the first frequency and a second control error based on a second component oscillating at the second frequency based on the monitoring result, and determines a control value for controlling the bias voltage using the first control error and the second control error.

Abstract: A variable optical attenuator includes: a transparent medium configured to transmit light; a first reflective film formed on a light incidence surface of the transparent medium; a second reflective film formed on a light emission surface of the transparent medium; and a resonance length variable medium configured to vary an optical resonance length between the first reflective film and the second reflective film, wherein the first reflective film has a first reflectivity at which at least one of light of a first wavelength and light of a second wavelength is partially transmitted through the first reflective film, the at least one of light being the light of the first wavelength, and wherein the second reflective film has a second reflectivity lower than the first reflectivity for the light of the first wavelength and a third reflectivity lower than the second reflectivity for the light of the second wavelength.

Abstract: A variable optical attenuator includes: a transparent medium configured to transmit light; a first reflective film formed on a light incidence surface of the transparent medium; a second reflective film formed on a light emission surface of the transparent medium; and a resonance length variable medium configured to vary an optical resonance length between the first reflective film and the second reflective film, wherein the first reflective film has a first reflectivity at which at least one of light of a first wavelength and light of a second wavelength is partially transmitted through the first reflective film, the at least one of light being the light of the first wavelength, and wherein the second reflective film has a second reflectivity lower than the first reflectivity for the light of the first wavelength and a third reflectivity lower than the second reflectivity for the light of the second wavelength.