Abstract: An optical waveguide element includes a substrate, an optical waveguide disposed inside the substrate or on the substrate, and an electrode provided along the optical waveguide, working on the optical waveguide to generate a phase change in a light wave propagating through the optical waveguide. The electrode is a traveling-wave electrode. In a modulation section where the light wave is controlled by the electrode, the electrode and the optical waveguide are configured so that the phase change generated in a first modulation section located within a predetermined distance range from a downstream side end portion along a propagation direction of a traveling wave of an electrical signal propagating through the electrode has a sign opposite to a sign of the phase change generated in a second modulation section located within a predetermined distance range from an input end of the electrical signal on an upstream side along the propagation direction.

Abstract: To provide a foreign-object system which uses a plurality of radars, and which can detect a foreign object that is present on a runway or the like and which can suppress interference between radars. A foreign-object detection system including a first radar 11, a second radar 21 connected to the first radar via a network 33, and a signal source 31 for transmitting a synchronization signal to the first radar and the second radar via the network, said foreign-object detection system wherein interference generated due to a radar signal outputted from the second radar being reflected by a reflective body and inputted to the first radar is prevented by controlling a delay time that corresponds to |?1i??2j|, where ?1i is the time taken for the synchronization signal to be transmitted from the signal source to the first radar, and ?2j is the time taken for the synchronization signal to be transmitted from the signal source to the second radar.

Abstract: [Problem] To provide a novel optical network which can be used as an in-vehicle optical backbone network and exhibits high capacity, low delay, low power consumption, low noise and low cost.

Abstract: [Problem] To provide a camera with high sensitivity even if an output to the outside is weak. [Solution] This camera includes a light source 3, a demultiplexing unit 5 which demultiplexes light from the light source 3 into first demultiplexed light and second demultiplexed light, a first modulator 7 which modulates the first demultiplexed light to obtain a modulated signal, an emission unit 9 which emits the modulation signal modulated by the first modulator 7, and a phase imparting means 11 which imparts a plurality of types of phase shifts to the second demultiplexed light to obtain phase-imparted local light.

Abstract: [Problem] To provide a novel optical network which can be used as an in-vehicle optical backbone network and exhibits high capacity, low delay, low power consumption, low noise and low cost.

Abstract: To provide a photodetector which enables reception of massively parallel optical communication, and with which a large volume of data for multi-mode transmission or multi-core transmission can be received instantaneously at once. A photodetector comprising a two-dimensional photodetector array in which a plurality of photodetectors 9 are arranged in a two-dimensional array, and which includes a wire 12 having a width of not more than 4 ?m between the plurality of photodetectors. Each of the photodetectors has a light reception area with a side measuring not more than 100 ?m. The plurality of photodetectors arranged in a two-dimensional array are spaced apart from each other by not less than 20 ?m.

Abstract: An extravisual obstacle detecting system includes: a radio wave receiving unit 15 configured to receives a radio wave from a radio wave source 13 attached to an object 11; one or a plurality of external sensors 19 attached to the vehicle 17 and configured to detect an external obstacle; an alarm generating unit 21 configured to generate a predetermined alarm, and, when the radio wave receiving unit 15 receives the radio wave from the object 11, and the external sensors 19 do not detect the object 11, the alarm generating unit 21 generates the first alarm.

Abstract: To provide a method and device capable of easily measuring the CMRR vs. frequency characteristics of an optical receiver. Light having a measurement frequency (? [hz]) is split into two different paths, and a first optical two-tone signal, which is signal light and has a frequency difference (???? [hz]), and a second optical two-tone signal, which is local light and has a frequency difference (?+?? [hz]), are obtained and input into a coherent receiver to be measured, wherein electrical signals output from the receiver are measured to obtain both the ratio of the intensity of a signal component having the frequency ???? [hz] to the intensity of a signal component having the frequency ? [hz], which corresponds to the CMRR on the signal light side, and the ratio of the intensity of a signal component having the frequency ?+?? [hz] to the intensity of the signal component having the frequency ? [hz], which corresponds to the CMRR on the local light side.

Abstract: To provide a method whereby a bias voltage capable of easily realizing a required extinction ratio can be controlled by utilizing a high-extinction ratio modulator even when a generic AD converter/control board is used, and a device for realizing the method. In the present invention, the step quantity (variation quantity) ?V of a control voltage is no more than 0.1 times the half-wave voltage V? [V]. For example, in the case of searching for the minimum point, the light intensity is measured when a bias that is larger by the step voltage ?V and a bias that is smaller by the step voltage ?V are applied, the current bias voltage being used as a reference, and the bias voltage is moved toward the smaller of the measured light intensities. The process of setting the moved bias voltage as a reference, comparing the light intensities for the bias points in both neighboring positions, and changing the reference bias voltage is then repeated.

Abstract: To provide a photodetector which enables reception of massively parallel optical communication, and with which a large volume of data for multi-mode transmission or multi-core transmission can be received instantaneously at once. A photodetector comprising a two-dimensional photodetector array in which a plurality of photodetectors 9 are arranged in a two-dimensional array, and which includes a wire 12 having a width of not more than 4 ?m between the plurality of photodetectors. Each of the photodetectors has a light reception area with a side measuring not more than 100 ?m. The plurality of photodetectors arranged in a two-dimensional array are spaced apart from each other by not less than 20 ?m.

Abstract: To provide a method whereby a bias voltage capable of easily realizing a required extinction ratio can be controlled by utilizing a high-extinction ratio modulator even when a generic AD converter/control board is used, and a device for realizing the method. In the present invention, the step quantity (variation quantity) ?V of a control voltage is no more than 0.1 times the half-wave voltage V? [V]. For example, in the case of searching for the minimum point, the light intensity is measured when a bias that is larger by the step voltage ?V and a bias that is smaller by the step voltage ?V are applied, the current bias voltage being used as a reference, and the bias voltage is moved toward the smaller of the measured light intensities. The process of setting the moved bias voltage as a reference, comparing the light intensities for the bias points in both neighboring positions, and changing the reference bias voltage is then repeated.

Abstract: To provide a method and device capable of easily measuring the CMRR vs. frequency characteristics of an optical receiver. Light having a measurement frequency (? [hz]) is split into two different paths, and a first optical two-tone signal, which is signal light and has a frequency difference (???? [hz]), and a second optical two-tone signal, which is local light and has a frequency difference (?-?? [hz]), are obtained and input into a coherent receiver to be measured, wherein electrical signals output from the receiver are measured to obtain both the ratio of the intensity of a signal component having the frequency ???? [hz] to the intensity of a signal component having the frequency ? [hz], which corresponds to the CMRR on the signal light side, and the ratio of the intensity of a signal component having the frequency ?+?? [hz] to the intensity of the signal component having the frequency ? [hz], which corresponds to the CMRR on the local light side.

Abstract: There is provided a photoelectric converter that converts an optical signal into an electrical signal for amplification, the photoelectric converter including a photoelectric conversion element that converts the optical signal into an electrical signal and outputs the electrical signal from an output terminal, a high-frequency amplifier that includes an input terminal of an electrical signal output from the output terminal and a DC cut-off capacitor which is disposed at an output stage of the input terminal and is serially connected to the input terminal and that amplifies the electrical signal, and an inductance element that is disposed between a bias power supply applying bias voltage or bias current to the photoelectric conversion element and the input terminal and which is connected in parallel to the DC cut-off capacitor.

Abstract: To provide a method for performing phase control of coherent two light wave signals while maintaining coherence in the state of the light signal, and a device which realizes such a method, there is provided, as illustrated in FIG. 1, a phase adjustment device 1 for two light waves including: a two light wave source 3, a wavelength separator 5, a first phase modulator 7, and a second phase modulator 9, whereby coherent two light waves are used as input signals to perform wavelength separation of those input signals thereafter to control optical phases of the respective light signals thereafter to multiplex them by using a multiplexer 11, thus to be able to obtain an output signal of which optical phase has been adjusted.

Abstract: An extravisual obstacle detecting system includes: a radio wave receiving unit 15 configured to receives a radio wave from a radio wave source 13 attached to an object 11; one or a plurality of external sensors 19 attached to the vehicle 17 and configured to detect an external obstacle; an alarm generating unit 21 configured to generate a predetermined alarm, and, when the radio wave receiving unit 15 receives the radio wave from the object 11, and the external sensors 19 do not detect the object 11, the alarm generating unit 21 generates the first alarm.

Abstract: To provide a self-homodyne detection communication system capable of using a space-division multiplexing signal as a signal for communication. The present invention relates to a space-division multiplexing apparatus 12 including a multi-core fiber 11 having multiple cores. The space-division multiplexing apparatus 12 uses cores other than a core 13 for self-homodyne detection among the multiple cores included in the multi-core fiber 11 as cores 16 for communication. The space-division multiplexing apparatus is configured to include a pilot-tone guiding unit 14 and a self-homodyne detection unit 15.

Abstract: The optical modulator includes optical modulation units. The plurality of optical modulation units is disposed in parallel on the same substrate. One input waveguide branches off to be connected to the Mach-Zehnder type optical waveguide of each optical modulation unit, and an entire optical waveguide is formed such that outputs from the Mach-Zehnder type optical waveguides are combined and output through one output waveguide. A modulation signal with the same intensity is applied to a modulation electrode of each optical modulation unit. In at least some of the optical modulation units, mechanical structures including the modulation electrodes of the optical modulation units are configured such that an amplitude value of an optical output modulated by the modulation signal of the optical modulation unit is ½n (n is a natural number) of a maximum amplitude value in other optical modulation units.

Abstract: A high-speed communication control system is provided to resolve the problem of transmission delay, while a communication capacity is ensured. A communication system includes a transmission station 13 and a reception station 15. A communication system 17 includes an optical fiber line 19 and a wireless path 21 that connect the transmission station 13 to the reception station 15 so that information is transmitted and received. The transmission station 13 includes a communication control unit 11 that controls a communication path. The reception station 15 is able to communicate with the transmission station 13. The communication control unit 11 controls whether the information is transmitted to the reception station 15 via one of the optical fiber line 19 and the wireless path 21.

Abstract: To provide a self-homodyne detection communication system capable of using a space-division multiplexing signal as a signal for communication. The present invention relates to a space-division multiplexing apparatus 12 including a multi-core fiber 11 having multiple cores. The space-division multiplexing apparatus 12 uses cores other than a core 13 for self-homodyne detection among the multiple cores included in the multi-core fiber 11 as cores 16 for communication. The space-division multiplexing apparatus is configured to include a pilot-tone guiding unit 14 and a self-homodyne detection unit 15.

Abstract: A method for evaluating a characteristic of, especially, each of Mach-Zehnder interferometers (MZIs) of an optical modulator. The method includes a step of measuring the intensity of the output of the optical modulator containing MZIs and a step of evaluating a characteristic of each MZI by using the sideband. The output intensity measuring step is the one of measuring the intensity Sn,k of the sideband signal contained in the output light from the optical modulator. The characteristic evaluating step is the one of evaluating a characteristic of the MZIk by using the Sn,k.