Abstract: A clock recovery apparatus for generating a recovery clock from received data may include, but is not limited to, first and second oscillators. The first oscillator generates a first signal having a first frequency. The first signal synchronizes with the received data when the received data has a first level. The second oscillator is connected in series to the first oscillator. The second oscillator generates a second signal as the recovery clock when the first signal has a second level. The second signal has a second frequency. The second signal synchronizes with the first signal.

Abstract: An optical packet network system of a ring type, capable of preventing degradation of an optical signal, can be implemented by providing a mechanism relatively simple in structure, capable of erasing light noise if the optical packet signal does not exists. In the optical packet network system made up by interconnecting respective nodes adjacent to each other, and connecting a sending source of an optical packet signal to a ring, a light noise removal function block is provided between the respective nodes adjacent to each other.

Abstract: An optical communication apparatus includes an erbium-doped optical fiber amplifier for amplifying a modulated optical signal, wherein a light which is not modulated is inputted to the erbium-doped optical fiber amplifier together with the optical signal.

Abstract: A fine vacuum tube element and other electronic elements are integrated and formed on a semiconductor substrate, and the fine vacuum tube element and the other electronic elements transmit signals to and from each other. When integrating the vacuum tube element with the other electronic elements, a quantum effect is realized in a room temperature environment by utilizing ballistic electrons (non-scattering electrons) traveling through the vacuum, and in the integrated circuit, an A/D converter is constructed by an interference system such as a Mach-Zehnder interferometer. Also an integrated circuit of an advanced function-integrated type is provided, comprising an interference system such as a Mach-Zehnder interferometer wherein weighting of the Mach-Zehnder interferometer is constituted for image processing and signal code conversion.

Abstract: There is provided an A/D converter capable of changing specification and function of the A/D converter with the use of a programmable circuit by combining comparators with the programmable circuit. The A/D converter comprises a parallel-connected comparison circuit including a plurality of comparators, an analog signal being inputted to one of input terminals of the respective comparators while respective predetermined reference voltages being inputted to the other of the input terminals of the respective comparators, and a digital processing circuit for receiving output signals from the parallel-connected comparison circuit, and executing predetermined digital processing as set on the basis of a program.

Abstract: An optical waveform shaping device includes a first waveguide portion, formed on a substrate, for transmitting the optical signal and simultaneously absorbing a portion of the optical signal, which has a signal level equal to or smaller than a predetermined value, so as to shape the optical signal; and a second waveguide portion, formed on the substrate, for transmitting the optical signal, which was transmitted through the first waveguide portion, and simultaneously amplifying the optical signal. The first waveguide portion may be formed using a saturable absorber. A first electrode for supplying electric current to the first waveguide portion so that the first waveguide portion is provided with a function of absorbing the optical signal; and a second electrode for supplying electric current to the second waveguide portion so that the second waveguide portion is provided with a function of amplifying the optical signal may also be provided.

Abstract: Disclosed is a repeater including: a recognizing unit to recognize a destination address of an optical packet from the optical packet which includes the destination address assigned in unit of bit and a bit indicating whether or not a plurality of destination addresses are assigned; an optical splitting unit to split the optical packet into a plurality of optical packets; and selecting units to select transmission channels for the split optical packets on the basis of recognition results by the recognizing units, respectively.

Abstract: A variable light signal delay apparatus includes a first delay optical fiber, a second delay optical fiber having a length different from the first delay optical fiber, and an optical switch having two input ports, two output ports, and paths, through which a light signal propagates, provided between the first delay optical fiber and the second delay optical fiber, in which a light signal input from at least one of the input ports propagated through either the first delay optical fiber or the second delay optical fiber or through neither the first delay optical fiber nor the second delay optical fiber to be output from a desired first output port.

Abstract: An object of this invention is to realize a pulse pattern generating apparatus that outputs a test signal of high waveform quality even when the shape of an eye pattern is changed. This invention is an improvement of a pulse pattern generating apparatus that generates a test signal of a predetermined pattern by using plural digital-analog converters and outputs the test signal to a test subject.

Abstract: An optical logic device performs a logic operation on a plurality of input light signals. The optical logic device has a photoelectric conversion portion, in which photoreceivers for receiving input light signals are provided in parallel, that outputs an electric signal obtained by adding up outputs of the photoreceivers, and a comparator that compares a voltage level of the electric signal outputted from the photoelectric conversion portion with a predetermined voltage level.

Abstract: A light modulating apparatus which is to be used in a transmission system using wavelength division multiplexing has: a signal generating section for producing a transmission signal and the like; a first light modulating section for modulating light emitted from a light source, on the basis of the transmission signal; a variable phase shifter which changes a phase of a light quantity control signal; a second light modulating section for modulating a light signal emitted from the first light modulating section, on the basis of an output of the variable phase shifter; a branching section for branching a light signal emitted from the second light modulating section, into an output light signal and an electric signal; and an analysis controlling section for sampling the electric signal, controlling the variable phase shifter on the basis of sampled data, and adjusting a timing of the modulation in the second light modulating section.

Abstract: A clock recovery apparatus for generating a recovery clock from received data may include, but is not limited to, first and second oscillators. The first oscillator generates a first signal having a first frequency. The first signal synchronizes with the received data when the received data has a first level. The second oscillator is connected in series to the first oscillator. The second oscillator generates a second signal as the recovery clock when the first signal has a second level. The second signal has a second frequency. The second signal synchronizes with the first signal.

Abstract: An optical switch changes over transmission paths of an optical signal by a refractive index change. The optical switch has an optical waveguide layer having an optical waveguide whose output path of an optical signal branches into two, and reflection diffusing ditches which are provided in a portion outside the optical waveguide in the optical waveguide layer, wherein the portion is closed to a branch portion of the optical waveguides. The reflection diffusing ditches extend in a direction crossing a traveling direction of the optical signal.

Abstract: A light signal switching apparatus has an input port and output ports, and outputs an output light from a desired output port. The apparatus has a splitter polarizing an input light into first and second polarized light whose polarization planes are different mutually by 90 degrees, a first polarization controller rotating a polarization plane of the second polarized light by 90 degrees to output a third polarized light, a first optical switch switching a path of the first polarized light to the desired output port side, a second optical switch switching a path of the third polarized light to the desired output port side, a second polarization controller rotating a polarization plane of the first polarized light by 90 degrees to output a fourth polarized light, and a combiner combining the third polarized light with the fourth polarized light, to output a combined light to the desired output port.

Abstract: An optical switch in which the adverse effect of heating can be restrained is realized.

Abstract: A phase control circuit includes: a variable delay circuit for delaying a clock signal; a first flip-flop circuit having a clock input terminal to which the delayed clock signal is input and a data input terminal to which a data signal is input; a second flip-flop circuit having a clock input terminal to which the data signal is input and a data input terminal to which the delayed clock signal is input; and an integration circuit for controlling a delay amount of the variable delay circuit based on an output signal of the second flip-flop circuit.

Abstract: An optical sampling apparatus has an electron beam generating apparatus which generates an electron beam by irradiating a cathode with an optical signal, a deflection electrode which deflects the generated electron beam, a sampling slit which transmits a part of the deflected electron beam, and a charge detection section which detects the quantity of charges or accumulated current of the transmitted electron beam. It is possible to perform accurate sampling in a high band.

Abstract: A light modulation apparatus including a Mach-Zehnder type light modulator, a driver for modulator outputting a control signal according to an input electric signal, a light branching circuit branching the output light signal, and a bias control circuit applying a bias voltage to the light modulator based on the branched light signal, the apparatus further comprises: a burst pause state detection circuit detecting a pause state of a burst signal included in the input electric signal; a photoelectric transducer converting an output light signal branched by the light branching circuit into an electric signal; a sampling circuit extracting the electric signal converted while the pause state is detected by the burst pause state; and a bias voltage adjustment circuit adjusting a bias voltage value of the bias voltage based on a voltage level of the extracted electric signal.

Abstract: An optical communication apparatus includes: an erbium-doped optical fiber amplifier for amplifying a modulated optical signal, wherein a DC (direct current) light which is not modulated is inputted to the erbium-doped optical fiber amplifier together with the optical signal.

Abstract: A light modulation apparatus including a Mach-Zehnder type light modulator, a driver for modulator outputting a control signal according to an input electric signal, a light branching circuit branching the output light signal, and a bias control circuit applying a bias voltage to the light modulator based on the branched light signal, the apparatus further comprises: a burst pause state detection circuit detecting a pause state of a burst signal included in the input electric signal; a photoelectric transducer converting an output light signal branched by the light branching circuit into an electric signal; a sampling circuit extracting the electric signal converted while the pause state is detected by the burst pause state; and a bias voltage adjustment circuit adjusting a bias voltage value of the bias voltage based on a voltage level of the extracted electric signal.