Abstract: An optical waveguide device includes a slot groove formed in a substrate; a pair of electrodes disposed in the slot groove; an electro-optic polymer material in the slot groove; and a step portion formed at an outer side of the slot groove, in a length direction of the slot groove.

Abstract: An optical module includes an optical device that outputs an optical signal corresponding to a control voltage, a voltage controller that applies the control voltage on which a dither signal is superimposed to the optical device, a monitor unit that monitors the optical signal output from the optical device, and outputs a monitor signal, a multiplier that multiplies the monitor signal by a reference signal corresponding to the dither signal, a filter unit that extracts a direct-current component included in a multiplication result, and a controller that causes the voltage controller to change the control voltage in accordance with the direct-current component. The controller changes the frequency of the dither signal or the reference signal such that the frequency of the reference signal is twice as large as that of the dither signal, when the direct-current component satisfies a predetermined condition.

Abstract: An optical modulator includes an optical waveguide, a first slab and a second slab. The optical waveguide is formed by filling polymer in a slot portion formed between a first rail and a second rail disposed in parallel to the first rail. The first slab includes a first partial slab electrically connected to a first electrode and a second partial slab that electrically connects the first rail and the first partial slab. In the first slab, a thickness dimension of the second partial slab is set small compared with that of the first rail. The second slab includes a third partial slab electrically connected to a second electrode and a fourth partial slab that electrically connects the second rail and the third partial slab. In the second slab, a thickness dimension of the fourth partial slab is set small compared with that of the second rail.

Abstract: An optical transmission device has a modulator, a first terminal groove, and relay groove. The modulator has a groove on a waveguide formed on a substrate. EO polymer is placed in the groove in the modulator. The modulator modulates light propagated through the waveguide by changing the phase of the light propagated through the waveguide through change of the refractive index of the EO polymer placed in the groove in the modulator by means of an electric signal. The first terminal groove is formed on the substrate and has a width larger than a width of the groove in the modulator. The relay groove is formed on the substrate and communicates with the groove in the modulator and the first terminal groove. Furthermore, the EO polymer is placed in the relay groove and the first terminal groove.

Abstract: An optical transmission device has a modulator, a first terminal groove, and relay groove. The modulator has a groove on a waveguide formed on a substrate. EO polymer is placed in the groove in the modulator. The modulator modulates light propagated through the waveguide by changing the phase of the light propagated through the waveguide through change of the refractive index of the EO polymer placed in the groove in the modulator by means of an electric signal. The first terminal groove is formed on the substrate and has a width larger than a width of the groove in the modulator. The relay groove is formed on the substrate and communicates with the groove in the modulator and the first terminal groove. Furthermore, the EO polymer is placed in the relay groove and the first terminal groove.

Abstract: An optical module includes an optical device that outputs an optical signal corresponding to a control voltage, a voltage controller that applies the control voltage on which a dither signal is superimposed to the optical device, a monitor unit that monitors the optical signal output from the optical device, and outputs a monitor signal, a multiplier that multiplies the monitor signal by a reference signal corresponding to the dither signal, a filter unit that extracts a direct-current component included in a multiplication result, and a controller that causes the voltage controller to change the control voltage in accordance with the direct-current component. The controller changes the frequency of the dither signal or the reference signal such that the frequency of the reference signal is twice as large as that of the dither signal, when the direct-current component satisfies a predetermined condition.

Abstract: An optical communication system includes an optical transmitter, and an optical receiver connected via a transmission line to the optical transmitter, in which system the optical transmitter transmits a continuous-wave light signal that enables beat detection when combined with a local oscillator signal in the optical receiver, and the optical receiver acquires a beat waveform through digital sampling by detecting the light signal using the local oscillator signal, performs frequency analysis on digitally sampled data having the beat waveform prior to demodulation, and controls the local oscillator frequency based upon the beat frequency.

Abstract: An optical transmitter includes an optical modulator to modulate light output from a light source with a drive signal, a monitor to detect an average value and an alternating-current (AC) component of output light intensity of the optical modulator, and a controller to select one of a first bias control and a second bias control in accordance with an amplitude of the drive signal. The first bias control controls a bias voltage of the drive signal based on the average value, and the second bias control controls the bias voltage of the drive signal based on the AC component.

Abstract: An optical receiver receives coherent light. The optical receiver includes an amplitude adjuster, a signal processor, and a controller. The amplitude adjuster adjusts amplitude of an input signal to output an analog signal. The signal processor receives a digital signal generated from the analog signal output from the amplitude adjuster, extracts clock components from the digital signal, and after establishing synchronization between the clock components and data components, extracts the data components from the digital signal to process the data components. The controller sets amplitude of the analog signal to first amplitude before establishment of synchronization by the digital signal, and changes the set amplitude to second amplitude that is smaller than the first amplitude after the establishment of synchronization.

Abstract: An optical transmitter includes: an optical modulator including a first modulation unit and a second modulation unit respectively configured to propagate a first optical signal and a second optical signal that are obtained by splitting input light; a signal generator configured to generate a first drive signal and a second drive signal that are respectively supplied to the first modulation unit and the second modulation unit; a phase controller configured to control a phase difference between the first optical signal and the second optical signal in the optical modulator; and a phase difference detector configured to detect the phase difference between the first optical signal and the second optical signal controlled by the phase controller. The signal generator generates the first drive signal and the second drive signal based on the phase difference detected by the phase difference detector.

Abstract: An optical transmitter includes an optical modulator to modulate light output from a light source with a drive signal, a monitor to detect an average value and an alternating-current (AC) component of output light intensity of the optical modulator, and a controller to select one of a first bias control and a second bias control in accordance with an amplitude of the drive signal. The first bias control controls a bias voltage of the drive signal based on the average value, and the second bias control controls the bias voltage of the drive signal based on the AC component.

Abstract: In an optical modulation device, a driver applies a drive signal based on a data signal to a modulation unit, the modulation unit modulates the light input from an LD by the drive signal, and a bias control unit calculates a bias voltage value so as to make the f0 element closer to “0,” according to a detection result in a synchronization detection unit, and supplies a bias voltage of the calculated voltage value to the modulation unit. The bias control unit stops ABC control when the data signal is in a state different from a predefined state during the ABC control, and, after the stop of the ABC control, restarts the ABC control using, as an initial value, a bias voltage value calculated before the stop of the ABC control.

Abstract: An optical receiver receives coherent light. The optical receiver includes an amplitude adjuster, a signal processor, and a controller. The amplitude adjuster adjusts amplitude of an input signal to output an analog signal. The signal processor receives a digital signal generated from the analog signal output from the amplitude adjuster, extracts clock components from the digital signal, and after establishing synchronization between the clock components and data components, extracts the data components from the digital signal to process the data components. The controller sets amplitude of the analog signal to first amplitude before establishment of synchronization by the digital signal, and changes the set amplitude to second amplitude that is smaller than the first amplitude after the establishment of synchronization.

Abstract: An optical communication system includes an optical transmitter, and an optical receiver connected via a transmission line to the optical transmitter, in which system the optical transmitter transmits a continuous-wave light signal that enables beat detection when combined with a local oscillator signal in the optical receiver, and the optical receiver acquires a beat waveform through digital sampling by detecting the light signal using the local oscillator signal, performs frequency analysis on digitally sampled data having the beat waveform prior to demodulation, and controls the local oscillator frequency based upon the beat frequency.

Abstract: An optical transmitter includes: an optical modulator including a first modulation unit and a second modulation unit respectively configured to propagate a first optical signal and a second optical signal that are obtained by splitting input light; a signal generator configured to generate a first drive signal and a second drive signal that are respectively supplied to the first modulation unit and the second modulation unit; a phase controller configured to control a phase difference between the first optical signal and the second optical signal in the optical modulator; and a phase difference detector configured to detect the phase difference between the first optical signal and the second optical signal controlled by the phase controller. The signal generator generates the first drive signal and the second drive signal based on the phase difference detected by the phase difference detector.

Abstract: An optical apparatus includes a collimation optical member for collimating and outputting input light, a condensing optical member for condensing light from the collimation optical member and a light blocking mask member provided at a place on an optical path of the input light for light blocking part of the input light, and enhances the degree of freedom in design of an optical system.

Abstract: In a wavelength selecting switch, light output from an input port of an input/output optical system is angularly dispersed according to a wavelength thereof, with a spectral element. Then the lights of respective wavelengths are collected by a light collecting optical system and reflected with a corresponding reflecting mirror of a mirror section. The reflected light corresponding to the angle of the reflecting mirror, is input to an output port at an output destination of the input/output optical system. The respective output ports of the input/output optical system each have a lens coupled to an end face of an optical fiber, and the lens has a structure where a focal length of a first region corresponding to inside a variable range of attenuation is different from a focal length of a second region corresponding to outside the variable range.

Abstract: In an optical apparatus according to the present invention, the lens thicknesses and curvature radiuses of respective first lenses are optimized so that beam waist positions of optical beams emitted from the respective first lenses of a lens array are independently changed according to aberration of a second lens, and the focal position deviation due to the aberration of the second lens is cancelled by a difference between the beam waist positions, which is given on the lens array side. As a result, it is possible to suppress, at a low cost, variations in focal positions of the optical beams which are emitted from respective ports of the lens array to be condensed by the common lens.

Abstract: An optical attenuator includes a first reflection portion reflecting a light incoming from an optical input portion in a direction different from incoming axis, a second reflection portion reflecting the light from the first reflection portion, an optical output portion outputting the light that is reflected by the first reflection portion after being reflected by the second reflection portion, and an optical-intensity-attenuation filter that is arranged on an optical path between the first reflection portion and the second reflection portion, optical transmittance being shifted in stages according to a position thereof. The first reflection portion is capable of turning to shift an incoming position at the optical-intensity-attenuation filter.

Abstract: The MEMS mirror, which has a reflective surface whose angle is variably changed, is provided with a portion whose reflectance is lowered than that of a center portion. The portion is provided in at least part of ends on a predetermined side of the MEMS mirror. As a result, a diffraction influence of light reflected by the end surfaces can be reduced at the time of angle change of the MEMS mirror.