Abstract: A superposition circuitry superposes a dither signal on a reference DC bias voltage and outputs a resultant voltage as a bias voltage to an MZ modulator, during control of a driving voltage amplitude. During the control of the driving voltage amplitude to the MZ modulator, an amplitude setter determines, by varying the amplitude of an output voltage from an amplifier, a plurality of amplitudes of output curves from a synchronous detector, each of which is obtained by varying the reference DC bias voltage output from a bias controller, and the amplitude setter sets the amplification factor of the amplifier, based on an amplitude of the output voltage from the amplifier that corresponds to an amplitude satisfying a predetermined condition, out of the plurality of the amplitudes of the output curves from the synchronous detector.

Abstract: A superposition circuitry superposes a dither signal on a reference DC bias voltage and outputs a resultant voltage as a bias voltage to an MZ modulator, during control of a driving voltage amplitude. During the control of the driving voltage amplitude to the MZ modulator, an amplitude setter determines, by varying the amplitude of an output voltage from an amplifier, a plurality of amplitudes of output curves from a synchronous detector, each of which is obtained by varying the reference DC bias voltage output from a bias controller, and the amplitude setter sets the amplification factor of the amplifier, based on an amplitude of the output voltage from the amplifier that corresponds to an amplitude satisfying a predetermined condition, out of the plurality of the amplitudes of the output curves from the synchronous detector.

Abstract: An optical modulation unit included in an optical transmitter includes two optical modulators that modulate each of two light beams based on applied bias voltages and input modulation signals, and an optical phase regulator that is connected to either of the two optical modulators, and regulates a phase of the light beam incident on the optical modulator. In a state where no modulation signal is input to the two optical modulators, while keeping bias voltages to be applied to one optical modulator and the optical phase regulator constant, the controller determines a first initial bias voltage such that an output light beam from the other optical modulator becomes zero. Thereafter, the controller determines a second initial bias voltage such that an output light beam from the one optical modulator becomes zero, while applying the first initial bias voltage to the other optical modulator.

Abstract: An optical modulation unit included in an optical transmitter includes two optical modulators that modulate each of two light beams based on applied bias voltages and input modulation signals, and an optical phase regulator that is connected to either of the two optical modulators, and regulates a phase of the light beam incident on the optical modulator. In a state where no modulation signal is input to the two optical modulators, while keeping bias voltages to be applied to one optical modulator and the optical phase regulator constant, the controller determines a first initial bias voltage such that an output light beam from the other optical modulator becomes zero. Thereafter, the controller determines a second initial bias voltage such that an output light beam from the one optical modulator becomes zero, while applying the first initial bias voltage to the other optical modulator.

Abstract: An optical transmitter includes: a data generating unit configured to generate a plurality of modulating signals; a driver configured to amplify the plurality of modulating signals generated by the data generating unit; a phase shifter configured to control a phase of at least one signal among the plurality of modulating signals to be input to the driver; a plurality of optical modulators connected in series to each other, and configured to modulate an optical signal on a basis of each of the modulating signals amplified by the driver; an optical coupler configured to branch the optical signal modulated by the optical modulator arranged at a last stage in the series; a photodiode configured to detect the optical signal branched by the optical coupler and convert the optical signal into an electric signal; and a phase control unit configured to control an amount of phase control of the phase shifter to maximize an intensity of the electric signal converted by the photodiode.

Abstract: An element carrier has a mounting surface where at least one element outputting a high-frequency signal is disposed. A first dielectric layer has a first side surface partially forming the mounting surface and a first main surface connecting to the first side surface and extending in an intersecting direction intersecting with the mounting surface. A first wiring pattern is provided on the first main surface and extends from the first side surface. A second dielectric layer has a second side surface partially forming the mounting surface and a second main surface connecting to the second side surface and extending in the intersecting direction, and is provided on a part of the first main surface of the first dielectric layer where the first wiring pattern is provided. A second wiring pattern is provided on the second main surface of the second dielectric layer and extends from the second side surface.

Abstract: An optical transmission apparatus in which, even if a change is made in the bit rate of modulation signals that are inputted to a plurality of optical modulating units, the modulation signals do not suffer from phase shifting, thereby enabling achieving synchronous modulation in the plurality of optical modulating units and enabling achieving a high optical signal quality. The optical transmission apparatus includes: a plurality of optical modulating units that modulate light on the basis of modulation signals; and a delay amount control unit that, based on bit rate information indicating a bit rate of the modulation signals, controls delay amounts of the modulation signals to be inputted to the plurality of optical modulating units, such that the light is modulated in a synchronous manner in the plurality of optical modulating units.

Abstract: An optical fiber sensor that can detect a liquid level or detect a property of liquid with high reliability even under a frequently vibrational environment. The optical fiber sensor includes an optical fiber that includes a core having an area where a grating is formed and a clad, the optical fiber being disposed so that at least a part of the area with the grating is immersed in liquid, a light source for making light incident to the optical fiber so that a cladding mode light having a wavelength band is generated by the grating, and a light receiving unit for detecting the intensity of light which is incident from the light source to the optical fiber and transmitted through the grating.

Abstract: An optical fiber sensor that can detect a liquid level or detect a property of liquid with high reliability even under a frequently vibrational environment. The optical fiber sensor includes an optical fiber that includes a core having an area where a grating is formed and a clad, and is disposed so that at least a part of the area with the grating is immersed in liquid, a light source for making light incident to the optical fiber so that a cladding mode light having a wavelength band is occurred by the grating, and a light receiving unit for detecting the intensity of light which is incident from the light source to the optical fiber and transmitted through the grating.

Abstract: A tunable dispersion compensator in which a heater portion can be easily constructed to reduce cost. A tunable dispersion compensator includes: an optical fiber having a grating portion; a heating unit for heating the grating portion to apply a temperature distribution to the grating portion; and a control unit for controlling the temperature distribution applied by the heating unit to control the group delay time characteristic of the grating portion. The heating unit includes: a heater including a single conductor having electrical resistors and which extends in a longitudinal direction of the grating portion over at least the entire length of the grating portion; and wirings electrically connected with the heater in respective positions along the longitudinal direction. The control unit supplies a voltage to each of the wirings.

Abstract: A tunable dispersion compensator in which a heater portion can be easily constructed to reduce cost. A tunable dispersion compensator includes: an optical fiber having a grating portion; a heating unit for heating the grating portion to apply a temperature distribution to the grating portion; and a control unit for controlling the temperature distribution applied by the heating unit to control the group delay time characteristic of the grating portion. The heating unit includes: a heater including a single conductor having electrical resistors and which extends in a longitudinal direction of the grating portion over at least the entire length of the grating portion; and wirings electrically connected with the heater in respective positions along the longitudinal direction. The control unit supplies a voltage to each of the wirings.