Abstract: The optical semiconductor device includes a spot-size converter formed on a semiconductor substrate. The spot-size converter has a multilayer structure including a light transition region. The multilayer structure includes a lower core layer, and an upper core layer having a refractive index higher than that of the lower core layer. The width of the upper core layer is gradually decreased and the width of the lower core layer is gradually increased in the light transition region. Both sides and an upper side of the multilayer structure are buried by a semi-insulating semiconductor layer in the light transition region. Light incident from one end section of the spot-size converter is propagated to the upper core layer. The light transits from the upper core layer to the lower core layer in the light transition region, is propagated to the lower core layer, and exits from the other end section thereof.

Abstract: An optical device includes a ridge-like optical waveguide portion, a mesa protector portion that is arranged in parallel to the optical waveguide portion, a resin portion that covers upper parts of the mesa protector portion and is disposed at both sides of the mesa protector portion, an electrode that is disposed on the optical waveguide portion, an electrode pad that is disposed on the resin portion located at an opposite side to the optical waveguide portion with respect to the mesa protector portion, and a connection portion that is disposed on the resin portion and electrically connects the electrode to the electrode pad.

Abstract: The I phase modulator modulates a phase based on the bias voltage in which a first modulation signal and a first pilot signal are inherent and the Q phase modulator modulates a phase based on the bias voltage in which a second pilot signal different from the first pilot signal and a second modulation signal are inherent. A time-average power synchronous detection unit detects an optical power at a timing at which the positivity and negativity of the voltages of both pilot signals become the same, and an optical power when the positivity and negativity of the voltages of both pilot signals are opposite. The bias voltage control unit controls the bias voltage so that the difference between both the optical powers becomes small based on the detection result of the time-average power synchronous detection unit.

Abstract: A light-receiving device array includes a photodiode array that is provided with plural light-receiving sections each of which includes a first conductivity type electrode and a second conductivity type electrode, and a carrier, wherein the carrier includes plural pair of electric lines each of which is formed from a first electric line connected to the first conductivity type electrode of each light-receiving section, and a second electric line connected to the second conductivity type electrode of the light-receiving section, a first ground electrode that extends between one pair of electric lines of the plural pair of electric lines and a pair of electric lines adjacent to the one pair of electric lines, and a second ground electrode that is formed on a part of the rear surface and is electrically connected to the first ground electrode.

Abstract: An optical transceiver has a projection covering member that can suppress EMI noise radiated from a pig-tail part. An elastic covering member covers a projection which includes an optical coupler of an optical sub assembly. The covering member is made of a conductive elastic material having a predetermined resistivity. At least a part of an outer circumference surface of the elastic covering member comes into intimate contact with an outer periphery of a conductive opening part of a case for the optical transceiver while an inner circumference surface of the elastic covering member comes into intimate contact with the projection.

Abstract: An optical phase shifter according to the invention includes the thermo-optical element of which a refractive index with respect to an input optical signal changes dependently on temperature; a temperature change section, having contact with one end of the thermo-optical element and of which a temperature changes so that a temperature of the thermo-optical element becomes a desired temperature; a heat dissipation section being disposed on an opposite side of the thermo-optical element with respect to the temperature change section and going into a state of thermal equilibrium at a temperature different from the temperature of the temperature change section; and a temperature buffer section, being disposed between the temperature change section and the heat dissipation section, having contact with the temperature change section and the heat dissipation section, and having a heat resistance greater than that of the heat dissipation section.

Abstract: A differential transmission circuit includes a grounded conductive layer, a pair of transmission line conductors, a conductive film and a via hole which connects the grounded conductive layer to the conductive film. The differential transmission circuit further includes a straight-line region which is present in the differential transmission circuit through which a differential transmission signal output by a driving circuit is transmitted and in which the pair of transmission line conductors extends parallel so as to have a first width, and a band rejection filter region in which the pair of transmission line conductors planarly overlaps the conductive film and extends parallel so as to have a second width narrower than the first width and a common mode of the differential transmission signal is attenuated at one of the frequencies which are natural number multiples of a frequency corresponding to the predetermined bit rate.

Abstract: To detect a wavelength drift of laser light with no error, an optical transmission module (10) includes: a laser diode (20); a laser temperature calculation section (52) for detecting the temperature of the laser diode (20) that monotonously increases with respect to a wavelength of the laser light; a wavelength calculation section (44) for detecting a transmittance of the laser light incident on an etalon filter (36) whose transmittance periodically varies with respect to the wavelength of the incident light, and a laser wavelength corresponding to the transmittance; and a wavelength error obtaining section (54) for detecting a wavelength error (wavelength drift), from a target wavelength, of the laser light output from the laser diode (20), based on the temperature detected by the laser temperature calculation section (52) and the laser wavelength detected by the wavelength calculation section (44).

Abstract: A differential transmission circuit includes a pair of transmission line conductors and a ground conductor layer, wherein the pair of transmission line conductors include a first straight line region where both the pair of transmission line conductors extend in parallel to each other in a first direction with a first width in a first layer, a first cross region where one of the pair of transmission line conductors is formed in the first layer, the other thereof is formed in a second layer, and the pair of transmission line conductors cross the each other in a three-dimensional manner, the first cross region being disposed on the front side of the first straight line region, and wherein each of the widths of the pair of transmission line conductors in the first cross region is smaller than the first width.

Abstract: A wavelength tunable filter and a wavelength tunable laser module are a codirectional coupler type whose characteristics do not vary significantly with a process error. They are structured so as to include a semiconductor substrate which has a first optical waveguide and a second optical waveguide. The first and the second optical waveguides are extended from a first side of the semiconductor substrate to an opposing second side thereof. The first optical waveguide includes a first core layer, which has a planar layout having periodic convexes and concaves, and a pair of electrodes, which vertically sandwich the first core layer. The second optical waveguide includes a second core layer, which has a lower refractive index than the first core layer. Further, a layer having the same composition and film thickness as the second core layer is placed under the first core layer.

Abstract: In pattern synchronization for correctly regenerating received data, which is performed in an optical receiver for receiving an optical signal that has been subjected to quadrature phase modulation, signal conduction is quickly established without using duplicate combinations of bit shifting and pattern changing. A control method that does not involve verifying the duplicate combinations generated in modulation formats and pattern synchronization search orders. Specifically, a signal check circuit (40) performs data verification of data multiplexed by a MUX circuit (38) for multiplexing two data strings, and a bit shift pattern change control circuit (41) controls a bit shift circuit (36) and a pattern changing circuit (37) based on a result of the data verification and detects a correct combination of correct regenerated data to establish the signal conduction. At this time, for the bit shift circuit (36) and the pattern changing circuit (37), the duplicate combinations are not verified.

Abstract: A delay interferometer includes a half beam splitter and two pentagonal prisms disposed on a substrate. The half beam splitter branches light to be measured which travels substantially in parallel with the substrate into two branched light beams. The pentagonal prisms respectively reflect the respective branched light beams such that the optical axes of the branched light beams are moved in parallel in a direction substantially perpendicular to the substrate by reflection. The half beam splitter combines the branched light beams reflected by the pentagonal prisms to generate interference light beams.

Abstract: Provided are an optical transmitter device and an optical transmitter module which are capable of reducing the optical transmitter module size while maintaining a state where an excellent optical transmission waveform quality is obtained over a wide range of frequencies. The optical transmission module (2) includes a semiconductor laser diode device (10), an optical modulator device (12), and a first termination resistor circuit (14-1). A printed circuit board (4) includes a driver IC (16) and a second termination resistor circuit (14-2). A lower cutoff frequency of the first termination resistor circuit (14-1) and an upper cutoff frequency of the second termination resistor circuit (14-2) correspond to each other. An impedance of the first termination resistor circuit (14-1) in a pass frequency band thereof and an impedance of the second termination resistor circuit (14-2) in a pass frequency band thereof correspond to each other.

Abstract: Disclosed is an optical transmission module in which effects of conductive heat from sides of a metal case upon a thermistor are reduced, thereby allowing steady optical beam wavelengths to be obtained over a wide range of temperatures, regardless of the temperature of the usage environment. Specifically, the optical transmission module includes Peltier elements disposed inside a metal case, a metal base disposed upon the Peltier elements, a laser diode substrate disposed upon the metal base, a laser diode disposed upon the laser diode substrate, a thermistor substrate disposed upon the metal base, a thermistor disposed upon the thermistor substrate, and a thermally conductive member, disposed in the vicinity of the thermistor, that has a height greater than the height of the thermistor.

Abstract: Provided is an optical module including: an optical assembly incorporating a light emitting or receiving device for converting one of an electrical signal and an optical signal into another of the electrical signal and the optical signal; a circuit board electrically connected to the optical assembly; an optical fiber optically connected to the optical assembly; a tray for winding the optical fiber therein and pulling out the optical fiber therefrom; and a case receiving the optical assembly, the circuit board, the optical fiber, and the tray. In the optical module, the tray is fixed with respect to the case so as to be reciprocatingly movable only within a restricted range, and the tray is moved from a position to another position within the restricted range so as to be moved away from an electrical connection section between the optical assembly and the circuit board.

Abstract: Provided is an optical module, including: an optical system having an optical path in a space thereof; an electro-optical device optically connected to a first input/output port as one of an input port and an output port of the optical system; an optical waveguide having flexibility; and a housing including an optical interface. The optical waveguide includes: a first connection portion optically connected to the optical interface in the housing; and a second connection portion optically connected to a second input/output port as another one of the input port and the output port of the optical system. The optical waveguide is arranged so as to be bent in the housing. A first optical axis passing between the optical interface and the first connection portion is displaced from a second optical axis passing between the second input/output port and the second connection portion.

Abstract: A wavelength tunable filter and a wavelength tunable laser module are a codirectional coupler type whose characteristics do not vary significantly with a process error. They are structured so as to include a semiconductor substrate which has a first optical waveguide and a second optical waveguide. The first and the second optical waveguides are extended from a first side of the semiconductor substrate to an opposing second side thereof. The first optical waveguide includes a first core layer, which has a planar layout having periodic convexes and concaves, and a pair of electrodes, which vertically sandwich the first core layer. The second optical waveguide includes a second core layer, which has a lower refractive index than the first core layer. Further, a layer having the same composition and film thickness as the second core layer is placed under the first core layer.

Abstract: Provided is an optical transmission circuit capable of realizing a high-quality optical signal waveform with low power consumption. An optical transmission circuit (10) includes: a laser diode (800); a modulator (900) for supplying a differential modulation current to an anode terminal and a cathode terminal of the laser diode (800) through transmission lines (301 to 304); a current source (101) for supplying a forward bias current to the laser diode (800); and a magnetic sheet (wave absorber) (400) disposed so as to cover at least a part of the transmission lines (303 and 304). An impedance of the laser diode (800) is lower than characteristic impedances of the transmission lines (301 to 304) which are formed so that the characteristic impedances thereof are matched to an output impedance of the modulator (900).

Abstract: In an InGaN-based nitride semiconductor optical device having a long wavelength (440 nm or more) equal to or more than that of blue, the increase of a wavelength is realized while suppressing In (Indium) segregation and deterioration of crystallinity. In the manufacture of an InGaN-based nitride semiconductor optical device having an InGaN-based quantum well active layer including an InGaN well layer and an InGaN barrier layer, a step of growing the InGaN barrier layer includes: a first step of adding hydrogen at 1% or more to a gas atmosphere composed of nitrogen and ammonia and growing a GaN layer in the gas atmosphere; and a second step of growing the InGaN barrier layer in a gas atmosphere composed of nitrogen and ammonia.

Abstract: Provided are an optical receptacle capable of manufacturing an optical module thereby, while suppressing a manufacturing cost, preventing a quality degradation, and suppressing a quantity of returning light by reflection. In the optical receptacle, a recess for receiving a lens and a lens support and a through-hole penetrating from a bottom of the recess toward an exterior are formed, and the recess is formed so that an inner peripheral surface of the recess is fixed to a desired position with respect to an outer peripheral surface of the lens support, in a case where the lens and the lens support are received in the recess such that an optical axis of the lens and an optical axis of the optical fiber to be inserted into the through hole are deviated from each other.