Abstract: An optical module includes a light source; a demultiplexer configured to demultiplex a light into a transmission light and a local light; an optical modulator; an excitation light source; an optical waveguide substrate that includes: a polarization beam splitter configured to split a reception light into an X-polarized component and a Y-polarized component, a beam splitter, a pair of optical hybrid circuits configured to cause the X-polarized component and the Y-polarized component to interfere with the local light split by the beam splitter, a pair of local light waveguides configured to couple the beam splitter and the pair of optical hybrid circuits, a pair of reception light waveguides configured to couple the polarization beam splitter and the pair of optical hybrid circuits, wherein the pair of local light waveguides and the transmission light waveguide are doped with a rare-earth ion that amplifies a light when the excitation light is introduced.

Abstract: An optical module includes a light source; a demultiplexer configured to demultiplex a light into a transmission light and a local light; an optical modulator; an excitation light source; an optical waveguide substrate that includes: a polarization beam splitter configured to split a reception light into an X-polarized component and a Y-polarized component, a beam splitter, a pair of optical hybrid circuits configured to cause the X-polarized component and the Y-polarized component to interfere with the local light split by the beam splitter, a pair of local light waveguides configured to couple the beam splitter and the pair of optical hybrid circuits, a pair of reception light waveguides configured to couple the polarization beam splitter and the pair of optical hybrid circuits, wherein the pair of local light waveguides and the transmission light waveguide are doped with a rare-earth ion that amplifies a light when the excitation light is introduced.

Abstract: An optical reception device includes an optical waveguide substrate that includes a polarization beam splitter that divides reception light into an X polarization component and a Y polarization component orthogonal to the X polarization component, a beam splitter that divides local light, a pair of optical hybrid circuits that causes each of the X polarization component and the Y polarization component to interfere with the divided local light, a first optical waveguide through which the reception light passes, a second optical waveguide through which the X polarization component passes, a third optical waveguide through which the Y polarization component passes, and a fourth optical waveguide through which the local light passes, wherein at least one of the first to fourth optical waveguides is doped with rare earth ions for amplifying light having a predetermined frequency when excitation light is introduced.

Abstract: An optical transmission device as the first optical transmission device includes a light source to output light, an optical transmitter to transmit first information regarding a reception characteristic and power consumption of the first optical transmission device to a second transmission device, an optical receiver to receive second information regarding a reception characteristic and power consumption of the second optical transmission device, an optical branching circuit to branch the light output from the light source into transmission light for the optical transmitter and local light for coherent reception by the optical receiver, and vary power of the transmission light and power of the local light individually, and a processor to control a driving condition of the optical branching circuit, based on the first information and the second information, the power of the transmission light and the power of the local light varying in accordance with the driving condition.

Abstract: An optical transmission device as the first optical transmission device includes a light source to output light, an optical transmitter to transmit first information regarding a reception characteristic and power consumption of the first optical transmission device to a second transmission device, an optical receiver to receive second information regarding a reception characteristic and power consumption of the second optical transmission device, an optical branching circuit to branch the light output from the light source into transmission light for the optical transmitter and local light for coherent reception by the optical receiver, and vary power of the transmission light and power of the local light individually, and a processor to control a driving condition of the optical branching circuit, based on the first information and the second information, the power of the transmission light and the power of the local light varying in accordance with the driving condition.

Abstract: A variable optical attenuator includes: a transparent medium configured to transmit light; a first reflective film formed on a light incidence surface of the transparent medium; a second reflective film formed on a light emission surface of the transparent medium; and a resonance length variable medium configured to vary an optical resonance length between the first reflective film and the second reflective film, wherein the first reflective film has a first reflectivity at which at least one of light of a first wavelength and light of a second wavelength is partially transmitted through the first reflective film, the at least one of light being the light of the first wavelength, and wherein the second reflective film has a second reflectivity lower than the first reflectivity for the light of the first wavelength and a third reflectivity lower than the second reflectivity for the light of the second wavelength.

Abstract: A polarization reducing apparatus includes a separating unit configured to separate input light into components having polarization directions orthogonal to each other; a winding waveguide of silicon formed on a silicon substrate in a winding manner, the winding waveguide transmitting a first component among the components separated by the separating unit; an optical path configured to have a shorter optical path length than the winding waveguide, the optical path transmitting a second component among the components separated by the separating unit; a combining unit configured to combine the first component and the second component; and an output unit configured to output light consisting of the first component and the second component combined by the combining unit.

Abstract: There is provided a transmission apparatus including: generators to generate optical signals having wavelengths included in a predetermined band, the wavelengths being variable; a transmitter to multiplex the optical signals and transmit the optical signals to another transmission apparatus; a memory; and a processor coupled to the memory and the processor to: monitor reception quality of an optical signal for monitoring received by the another transmission apparatus while changing a wavelength of the optical signal for monitoring which is generated by the generators, determine a first wavelength of a first optical signal having a longest wavelength and a second wavelength of a second optical signal having a shortest wavelength, based on the reception quality monitored, determine a wavelength of an optical signal except for the first and second optical signals, based on the first second wavelengths, and control the wavelength generated by the generators, based on the wavelength determined.

Abstract: In an optical receiver, a first optical filter (one of a long-pass optical filter and a short-pass optical filter) is provided on an optical incident surface of a light collection device. A second optical filter (the other one of the long-pass optical filter and the short-pass optical filter) is provided on an optical reception surface of a light reception device.

Abstract: A laser device includes: a semiconductor laser; a detection circuit which detects optical power in each position of a spot of emission light which is emitted from the semiconductor laser; and a determination circuit which calculates a power distribution of the spot of the emission light and total power of the spot based on the optical power detected by the detection circuit to determine a sudden death failure sign of the semiconductor laser based on the calculated power distribution and the total power.

Abstract: An optical device includes a first fiber; a liquid crystal member configured to have liquid crystal pixels that reflect light output from the first fiber; a second fiber configured to have a core to which a first order light ray in the light reflected by the liquid crystal member is optically connected; a light receiving circuit configured to receive higher order light rays in the light reflected by the liquid crystal member; and a control circuit configured to control based on a light receiving result of the light receiving circuit, efficiency of optical connection of the first order light ray to the core of the second fiber, by varying an angle of the light reflected by the liquid crystal member.

Abstract: A semiconductor laser device includes: a semiconductor laser that contains aluminum or gallium arsenide in an active layer; a detector that detects a shift of a wavelength of emission light from the semiconductor laser toward a short wavelength side; and a judger that makes a judgment about a sign of a sudden failure of the semiconductor laser based on a detection result by the detector.

Abstract: A polarization reducing apparatus includes a separating unit configured to separate input light into components having polarization directions orthogonal to each other; a winding waveguide of silicon formed on a silicon substrate in a winding manner, the winding waveguide transmitting a first component among the components separated by the separating unit; an optical path configured to have a shorter optical path length than the winding waveguide, the optical path transmitting a second component among the components separated by the separating unit; a combining unit configured to combine the first component and the second component; and an output unit configured to output light consisting of the first component and the second component combined by the combining unit.

Abstract: An optical device includes a first fiber; a liquid crystal member configured to have liquid crystal pixels that reflect light output from the first fiber; a second fiber configured to have a core to which a first order light ray in the light reflected by the liquid crystal member is optically connected; a light receiving circuit configured to receive higher order light rays in the light reflected by the liquid crystal member; and a control circuit configured to control based on a light receiving result of the light receiving circuit, efficiency of optical connection of the first order light ray to the core of the second fiber, by varying an angle of the light reflected by the liquid crystal member.

Abstract: A variable optical attenuator includes: a transparent medium configured to transmit light; a first reflective film formed on a light incidence surface of the transparent medium; a second reflective film formed on a light emission surface of the transparent medium; and a resonance length variable medium configured to vary an optical resonance length between the first reflective film and the second reflective film, wherein the first reflective film has a first reflectivity at which at least one of light of a first wavelength and light of a second wavelength is partially transmitted through the first reflective film, the at least one of light being the light of the first wavelength, and wherein the second reflective film has a second reflectivity lower than the first reflectivity for the light of the first wavelength and a third reflectivity lower than the second reflectivity for the light of the second wavelength.

Abstract: A polarization reducing apparatus includes a separating unit configured to separate input light into components having polarization directions orthogonal to each other; a winding waveguide of silicon formed on a silicon substrate in a winding manner, the winding waveguide transmitting a first component among the components separated by the separating unit; an optical path configured to have a shorter optical path length than the winding waveguide, the optical path transmitting a second component among the components separated by the separating unit; a combining unit configured to combine the first component and the second component; and an output unit configured to output light consisting of the first component and the second component combined by the combining unit.

Abstract: An optical amplification repeater includes a first rare-earth-doped optical amplification medium which amplifies a first signal light to be transmitted to a downstream, a second rare-earth-doped optical amplification medium which amplifies a second signal light to be transmitted to an upstream, and a pump light split and guide unit configured to split a pump light transmitted together with any of the first and second signal lights and to guide the split pump light to each of the first and second rare-earth-doped optical amplification mediums.

Abstract: An amplifying apparatus includes an optical fiber that includes a wound portion doped with a rare earth element and three-dimensionally wound, holes being formed in cladding of the optical fiber and surrounding a core of the optical fiber, the optical fiber transmitting signal light injected thereinto; a thermally conductive member in which the wound portion of the optical fiber embedded, the thermally conductive member having thermal conductivity; a light source that emits excitation light; an injecting unit that injects the excitation light emitted by the light source, into the optical fiber; and a temperature adjusting unit that includes a thermal coupling unit thermally connected to the light source and the thermally conductive member, the temperature adjusting unit adjusting a temperature of the thermal coupling unit.

Abstract: An optical transmission medium includes: a plurality of cores; a first cladding that covers each of the plurality of cores; a second cladding that covers a plurality of first claddings; and a reflection layer that covers the second cladding and has reflection characteristics with respect to a wavelength band of multimode light.

Abstract: An optical transmission medium includes: a plurality of cores; a first cladding that covers each of the plurality of cores; a second cladding that covers a plurality of first claddings; and a reflection layer that covers the second cladding and has reflection characteristics with respect to a wavelength band of multimode light.