Abstract: An optical module of one embodiment includes a semiconductor modulator having a rectangular planar shape, an input lens system facing the input port, a first output lens system facing the first output port, a second output lens system facing the second output port, a first monitor element facing the first monitor port, a second monitor element facing the second monitor port, a first polarizer disposed between the first monitor port and the first monitor element, and a second polarizer disposed between the second monitor port and the second monitor element.

Abstract: A method of manufacturing an optical semiconductor element includes: stacking a plurality of compound semiconductor layers on a first substrate containing a compound semiconductor; dividing the first substrate into small pieces; forming terraces, grooves, walls, and a first mesa for a waveguide on a second substrate containing silicon; jointing at least one small piece to the second substrate after the forming; wet-etching the first substrate so as to expose the compound semiconductor layers after the jointing; and forming a second mesa opposite to the first mesa from the compound semiconductor layers; wherein the grooves are formed on both sides of the first mesa, the terraces are formed on both sides of the first mesa and the grooves, and the walls are arranged in an extending direction of each groove.

Abstract: A method of manufacturing an optical semiconductor element includes: stacking a plurality of compound semiconductor layers on a first substrate containing a compound semiconductor; dividing the first substrate into small pieces; forming terraces, grooves, walls, and a first mesa for a waveguide on a second substrate containing silicon; jointing at least one small piece to the second substrate after the forming; wet-etching the first substrate so as to expose the compound semiconductor layers after the jointing; and forming a second mesa opposite to the first mesa from the compound semiconductor layers; wherein the grooves are formed on both sides of the first mesa, the terraces are formed on both sides of the first mesa and the grooves, and the walls are arranged in an extending direction of each groove.

Abstract: A semiconductor optical modulator includes optical input and output portions; a plurality of Mach-Zehnder modulators, each including first and second waveguide arms having first and second modulation electrodes, respectively; an optical demultiplexer coupled between the optical input portion and the Mach-Zehnder modulators through an optical waveguide; an optical multiplexer coupled between the optical output portion and the Mach-Zehnder modulators; a plurality of electrical inputs; and a plurality of differential transmission lines electrically connecting the electrical inputs to the Mach-Zehnder modulators. The first modulation electrode and the second modulation electrode of at least one of the Mach-Zehnder modulators, one of the electrical inputs, and one of the differential transmission lines that connects such one electrical input to such one Mach-Zehnder modulator form an electrical circuit having a differential impedance in a range of 80? to 95?.

Abstract: A semiconductor optical modulator includes optical input and output portions; a plurality of Mach-Zehnder modulators including first and second waveguide arms having first and second modulation electrodes, respectively; an optical demultiplexer coupled between the optical input portion and the Mach-Zehnder modulator through an optical waveguide; an optical multiplexer coupled between the optical output portion and the Mach-Zehnder modulator; a plurality of electrical inputs including first, second, and common electrodes disposed between the first and second electrodes; and a plurality of differential transmission lines electrically connecting the electrical inputs to the Mach-Zehnder modulators. The Mach-Zehnder modulators, the optical demultiplexer, the optical multiplexer, the electrical inputs, and the differential transmission lines are disposed on a single substrate.

Abstract: An optical modulation apparatus including: a Mach-Zehnder optical modulator having two optical waveguides, two output optical waveguides and a join-and-branch portion; a phase adjustment circuit configured to output a phase control signal to phase adjustment electrodes provided respectively on the two optical waveguides; a drive circuit configured to output a modulation signal to modulation electrodes provided respectively on the two optical waveguides as a differential signal, the modulation signal modulating lights propagated in the two optical waveguides; and a signal polarity reversal circuit configured to reverse a polarity of the differential signal to be output from the drive circuit.

Abstract: An optical modulation apparatus including: a Mach-Zehnder optical modulator having two optical waveguides, two output optical waveguides and a join-and-branch portion; a phase adjustment circuit configured to output a phase control signal to phase adjustment electrodes provided respectively on the two optical waveguides; a drive circuit configured to output a modulation signal to modulation electrodes provided respectively on the two optical waveguides as a differential signal, the modulation signal modulating lights propagated in the two optical waveguides; and a signal polarity reversal circuit configured to reverse a polarity of the differential signal to be output from the drive circuit.

Abstract: An optical unit is disclosed, in which the optical unit provides four optical devices each of which corresponds to a specific wavelength different from each other. In the transmitter unit, the unit includes two optical modules each including two optical devices and one filter unit with a polarization beam filter. The optical beam form two optical devices are combined by the polarization beam filter, while the optical output from the optical modules are combined with the thin film filter.

Abstract: A method of manufacturing an optical waveguide device that is capable of reducing the imbalance in the refractive index profile of a core, and an optical waveguide device that has the reduced imbalance in the refractive index profile are provided. The method of manufacturing an optical waveguide device has the steps of forming a groove in a first cladding layer having a first dopant that lowers the refractive index of the first cladding layer below the refractive index of pure silica glass, forming a core in the groove, and forming a second cladding layer having a second dopant that lowers the refractive index of the second cladding layer below the refractive index of pure silica glass, over the first cladding layer and the core.

Abstract: A method of manufacturing an optical waveguide device with low scattering loss is provided. This method comprises, in the following order, the steps of forming a groove by etching in a cladding member having a glass region including a first dopant that lowers the softening temperature of the glass region, heat treating the cladding member at a temperature that is higher than the lowered softening temperature, forming a core within the groove, and forming an overcladding layer composed of glass including a second dopant over the core and the cladding member. Alternatively, this method comprises the steps of forming a groove by etching in a cladding member having a glass region including one of elemental germanium, elemental phosphorus, and elemental boron, heat treating the cladding member after the formation of the groove, forming a core within the groove, and forming an overcladding layer over the core and the cladding member.

Abstract: A method of manufacturing an optical waveguide device that is capable of reducing the imbalance in the refractive index profile of a core, and an optical waveguide device that has the reduced imbalance in the refractive index profile are provided. The method of manufacturing an optical waveguide device has the steps of forming a groove in a first cladding layer having a first dopant that lowers the refractive index of the first cladding layer below the refractive index of pure silica glass, forming a core in the groove, and forming a second cladding layer having a second dopant that lowers the refractive index of the second cladding layer below the refractive index of pure silica glass, over the first cladding layer and the core.

Abstract: In a method of manufacturing an optical waveguide device, the surface of a core can be planarized in a concaving process. In this manufacturing method, a plasma CVD apparatus having a coil for producing plasma and a table for mounting products is used. In the method, a first cladding having a concavity is mounted on the table, a core film is formed on the first cladding while high-frequency electric power P1 is supplied to the coil and high-frequency electric power P2 is supplied to the table, a resist film is formed on the core film, a core is formed in the concavity by etching the resist film and the core film, and a second cladding is formed on the first cladding and the core.

Abstract: A cable and cable system is provided having a conductor and an insulation layer on an outer circumference of a conductor. The insulation layer is impregnated with a medium-viscosity insulating oil that has a viscosity of 10 centistokes (cst) to less than 500 cst at 60° C. The insulation layer includes an insulating tape that may be one or a combination of composite tape having a polyolefin resin film laminated with a kraft paper on both its sides and an insulating tape including a polyolefin resin film. The cable includes a metal sheath provided on an outer circumference of the insulation layer, and a reinforcing layer formed on an outer circumference of the metal sheath. The reinforcing layer reinforces the metal sheath by absorbing hoop stress exerted on the metal sheath. The cable system includes a submarine-portion cable and a land-portion cable, an oil stop joint box, and an oil feeding tank.

Abstract: A solid cable provided with an insulation layer on the outer circumference of a conductor, and impregnated with insulating oil in this insulation layer. Medium-viscosity insulating oil the viscosity of which is between not less than 10 cst and less than 500 cst at 60° C. is used as the insulating oil.