Abstract: A high-frequency circuit is configured so as to include a printed circuit board and a flexible circuit board connected to the printed circuit board, wherein the printed circuit board includes: a first dielectric layer having a first surface and a second surface, a first ground conductor being formed on the first surface; a second dielectric layer having a third surface and a fourth surface, a second ground conductor being formed on the fourth surface; and first signal lines wired between the second surface and the third surface, the flexible circuit board includes: a third dielectric layer having a fifth surface and a sixth surface, a third ground conductor being formed on the fifth surface; a fourth dielectric layer having a seventh surface and an eighth surface, a fourth ground conductor being formed on the eighth surface; and second signal lines wired between the sixth surface and the seventh surface.

Abstract: An optical receiver includes: a support base; a waveguide-type light receiving element fixed to a surface of the support base; and an optical circuit element fixed to the surface of the support base, wherein the waveguide-type light receiving element includes: a semi-insulating semiconductor substrate; a light absorbing layer formed on one main surface of the semiconductor substrate and has a pair of joint surfaces perpendicular to the one main surface of the semiconductor substrate and an incident end face on which light is incident and which has facing end sides of the joint surfaces as a pair of opposite sides, the incident end face having a layer thickness longer than a layer width; an n-type semiconductor layer joined to one of the joint surfaces of the light absorbing layer, and a p-type semiconductor layer joined to the other of the joint surfaces of the light absorbing layer.

Abstract: A metal stem includes a cylindrical portion in which an FPC inserting portion is formed, and a base standing upright from one plane of the cylindrical portion. A tubular lens cap with one open end is fixed to a peripheral portion of the one plane of the cylindrical portion, and has a lens mounted on a bottomed portion. A substrate mounted on one plane of the base includes a signal wiring layer and a ground wiring layer. An optical semiconductor element is mounted on the substrate and has a signal terminal connected to the signal wiring layer of the substrate, and a ground terminal connected to the ground wiring layer of the substrate. An FPC substrate is disposed so as to pass through the FPC inserting portion and to face the one plane of the base. The FPC substrate includes a signal wiring layer connected to the signal wiring layer of the substrate with a metal wire.

Abstract: An optical scanning device includes an optical mode converter to change, in accordance with a change in wavelength of a light output from a light source or phase of the light output from the light source, a radiation direction of the light, and an actuator to rotate the optical mode converter about each of two shafts orthogonal to each other.

Abstract: Included are a transmitter and a receiver caused to have a constant temperature.

Abstract: An optical module includes: a first lens and a second lens provided between a light emitter and a light receiver; and a base member on which the light emitter and the light receiver are placed, and each of the first lens and the second lens is fixed via an adhesive resin. A first bonding direction in which a first bonding surface of the first lens is bonded and fixed via an adhesive resin, and a second bonding direction in which a second bonding surface of the second lens is bonded and fixed via an adhesive resin are respectively perpendicular to an optical axis direction of light, and an orientation of the first bonding surface and an orientation of the second bonding surface make are different from each other.

Abstract: A metal stem includes a cylindrical portion in which an FPC inserting portion is formed, and a base standing upright from one plane of the cylindrical portion. A tubular lens cap with one open end is fixed to a peripheral portion of the one plane of the cylindrical portion, and has a lens mounted on a bottomed portion. A substrate mounted on one plane of the base includes a signal wiring layer and a ground wiring layer. An optical semiconductor element is mounted on the substrate and has a signal terminal connected to the signal wiring layer of the substrate, and a ground terminal connected to the ground wiring layer of the substrate. An FPC substrate is disposed so as to pass through the FPC inserting portion and to face the one plane of the base. The FPC substrate includes a signal wiring layer connected to the signal wiring layer of the substrate with a metal wire.

Abstract: A high-frequency circuit is configured so as to include a printed circuit board and a flexible circuit board connected to the printed circuit board, wherein the printed circuit board includes: a first dielectric layer having a first surface and a second surface, a first ground conductor being formed on the first surface; a second dielectric layer having a third surface and a fourth surface, a second ground conductor being formed on the fourth surface; and first signal lines wired between the second surface and the third surface, the flexible circuit board includes: a third dielectric layer having a fifth surface and a sixth surface, a third ground conductor being formed on the fifth surface; a fourth dielectric layer having a seventh surface and an eighth surface, a fourth ground conductor being formed on the eighth surface; and second signal lines wired between the sixth surface and the seventh surface, and a connecting portion between the printed circuit board and the flexible circuit board includes: a plur

Abstract: Included are a transmitter and a receiver caused to have a constant temperature.

Abstract: An optical transmission apparatus (100) includes an optical transmitter (200) including an optical modulator (220) and an observation optical modulator (230) that attenuate optical power of input continuous wave light by an electro-absorption effect and output the continuous wave light. The optical modulator (220) performs pulse amplitude modulation on the continuous wave light and outputs the optical signal.

Abstract: An optical module includes: a first lens and a second lens provided between a light emitter and a light receiver; and a base member on which the light emitter and the light receiver are placed, and each of the first lens and the second lens is fixed via an adhesive resin. A first bonding direction in which a first bonding surface of the first lens is bonded and fixed via an adhesive resin, and a second bonding direction in which a second bonding surface of the second lens is bonded and fixed via an adhesive resin are respectively perpendicular to an optical axis direction of light, and an orientation of the first bonding surface and an orientation of the second bonding surface make are different from each other.

Abstract: An optical transmission apparatus includes an optical transmitter including an optical modulator and an observation optical modulator that attenuate optical power of input continuous wave light by an electro-absorption effect and output the light. The optical modulator performs pulse amplitude modulation on the continuous wave light and outputs the optical signal. The apparatus also includes: a bias voltage generation unit that generates a direct-current bias voltage and outputs the direct-current bias voltage to the optical modulator and the observation optical modulator; a modulation signal generation unit that generates an electrical signal for pulse amplitude modulation and outputs the electrical signal to the optical modulator; and a bias voltage control unit that instructs the bias voltage generation unit to adjust the direct-current bias voltage on the basis of an absorption amount of optical power in the optical modulator and an absorption amount of optical power in the observation optical modulator.

Abstract: An optical receiver to receive a multilevel modulation signal in which a value of transmission data is assigned to plural signal levels, the optical receiver including a clock generator to generate a recovered clock signal from the multilevel modulation signal when the clock generator detects that a signal level of the multilevel modulation signal transitions between two median levels of the signal levels, and a data identifier to identify a value of the transmission data by using the generated recovered clock signal and the multilevel modulation signal.

Abstract: A terminal portion configured to obtain electrical connection with a printed circuit board includes a first signal pad that is formed in a first conductor layer and is electrically separated from a ground layer, a pair of first ground pads that is formed in the first conductor layer to sandwich the first signal pad and is connected to the ground layer, a second signal pad that is formed in a second conductor layer and is connected to a signal line, a pair of second ground pads that is formed in the second conductor layer to sandwich the second signal pad and is electrically separated from the signal line, a third signal pad formed in a third conductor layer, and a pair of third ground pads formed in the third conductor layer to sandwich the third signal pad. The second signal pad is wider than the third signal pad.

Abstract: A metal stem is provided with a through-hole, a temperature control module is mounted thereon, and a metal protrusion is formed integrally therewith. A lead pin includes a through section inserted in the through-hole of the metal stem, and an inner lead section continued from one end of the through section and extending up to the tip. The temperature control module is thermally connected to a semiconductor optical modulation element that is electrically connected to the inner lead section. The protrusion faces the inner lead section.

Abstract: An optical receiver is provided with a photoelectric converter that outputs an electrical signal according to light that is received by a light-receiving region. The optical receiver is provided with a condensing lens and optical filter that are located in an optical path from where signal light enters towards the light-receiving region. The condensing lens condenses the signal light onto the light-receiving region. The optical filter reflects light having a first wavelength that is included in the signal light using a front surface thereof and reflects light having a second wavelength that is included in the signal light using a rear surface thereof that faces the front surface so that the light is emitted through the front surface.

Abstract: A terminal portion configured to obtain electrical connection with a printed circuit board includes a first signal pad that is formed in a first conductor layer and is electrically separated from a ground layer, a pair of first ground pads that is formed in the first conductor layer to sandwich the first signal pad and is connected to the ground layer, a second signal pad that is formed in a second conductor layer and is connected to a signal line, a pair of second ground pads that is formed in the second conductor layer to sandwich the second signal pad and is electrically separated from the signal line, a third signal pad formed in a third conductor layer, and a pair of third ground pads formed in the third conductor layer to sandwich the third signal pad. The second signal pad is wider than the third signal pad.

Abstract: An optical receiver is provided with a photoelectric converter that outputs an electrical signal according to light that is received by a light-receiving region. The optical receiver is provided with a condensing lens and optical filter that are located in an optical path from where signal light enters towards the light-receiving region. The condensing lens condenses the signal light onto the light-receiving region. The optical filter reflects light having a first wavelength that is included in the signal light using a front surface thereof and reflects light having a second wavelength that is included in the signal light using a rear surface thereof that faces the front surface so that the light is emitted through the front surface.