Other

National Institute of Information and Communications Technology, Incorporated Administrative Agency

Kokusai Denshin Denwa Kabushiki Kaisha

Nippon Steel Corporation

Kokusai Denshin Denwa Co., Ltd.

Kdd Corporation

Communications Research Laboratory, Independent Administrative Institution

Mitsubishi Denki Kabushiki Kaisha

Tetsuya Miyazaki

Shu Yamamoto

Noboru Edagawa

Tomohiro Otani

Naoki Kobayashi

Takashi Mizuochi

Tadayoshi Kitayama

Shiro Ryu

Isao Nakamura

Hiroshi Ichibangase

Aritomo Uemura

Kunitoshi Watanabe

Masahiro Masuda

Yukiyoshi Kamio

Yoichi Sashihara

Takatomi Kabashima

Kazuhiro Sekimoto

Masatoshi Suzuki

Hisato Uetsuka

Minoru Yoshida

Kiwami Matsushita

Yasuyuki Nagao

Yoshio Karasawa

Koichi Maru

Toshikazu Gozen

Yojiro Osaki

Tadayoshi Mitsubishi Denki Kitayama

Aritomo Mitsubishi Denki Uemura

Takashi Mitsubishi Denki Mizuochi

Hiroshi Mitsubishi Denki Ichibangase

An optical transmitter generates a transmission signal having a frame as a unit, the frame including a single optical pilot signal with a constant optical phase and a plurality of phase-modulated optical data signals, and outputs the transmission signal into a transmission line. In a receiver, a splitter splits the optical signal input from the transmission line. On a second arm of a Mach-Zehnder interferometer, an optical gate transmits the optical pilot signal and a duplicator duplicates the optical pilot signal output from the optical gate at predetermined time intervals. A balanced optical receiver converts the interfered optical signal output from the interferometer into an electrical signal. A gate and a discriminator extract the data from the electrical signal output from the receiver.

Method and apparatus for receiving data

An optical transmitter generates a transmission signal having a frame as a unit, the frame including a signal pilot signal with fixed amplitude and phase and two data bits to output the generated signal into a transmission line. In a receiver, a splitter splits the signal light from the transmission line. An optical delay delays the signal light for a 1-bit period. A first combiner combines the signal light from the transmission line and the output signal light from the optical delay. A photodetector converts the combined light into an electrical signal. A 3-bit optical delay, a second combiner, a BPF, and an oscillator generate a frame-timing signal. A gate separates a data from the output from the photodetector under the control of a gate control unit. A binary discriminator binary-discriminates the output signal from the gate.

Data transmission method and a system thereof

An optical multilevel-coded signal transmission system transmits information from an optical transmitter to an optical receiver through an optical transmission line using optical intensity and optical phase separately. The optical transmitter includes an inverted RZ signal light generator to generate an inverted RZ signal light intensity-modulated with a first data, and an optical phase modulator to phase-modulate the inverted RZ signal light according to a second data. The optical receiver includes a splitter to split a light input from the optical transmission line into first and second portions, an inverter to invert the first portion from the splitter, a first detector to detect the first data in the first portion inverted by the inverter, a converter to convert a phase-modulated signal included in the second portion from the splitter into an optical intensity-modulated signal, and a second detector to detect the second data in the optical intensity-modulated signal from the converter.

Optical multilevel-coded signal transmission system and method thereof, optical transmitter, and multilevel-coded signal light generating method

According the invention, a multiplexed light composed of a signal light of a signal wavelength, and a first route control light of a first route control wavelength different from the signal wavelength or a second route control light of a second route control wavelength different from the signal light and the first route control wavelength is incident to a demultiplexer. The demultiplexer demultiplexes the signal light of the signal wavelength, the first route control light, and the second route control light from the multiplexed light. An interferometer optical switch outputs the signal light from first output port according to the first route control light, and outputs the signal light from second output port according to the second route control light.

Optical router

An optical transmitter splits a linear polarization optical carrier into a TE wave and a TM wave. One of the TE wave and the TM wave is phase-modulated with a transmission data so as to generate a phase-modulated signal. The phase-modulated signal and the other one of the TE wave and the TM wave are coupled with a linear polarization and output into an optical transmission line. An optical receiver splits a light input from the optical transmission line into the TE wave and the TM wave. The TM wave or TE wave is converted into the TE wave or TM wave to interfere with the TE wave or TM wave. The interfered signal light is converted into an electric signal for restoration of the data.

Optical transmission method and system

An optical receiver including an optical divider to divide a signal light from an optical transmission line into two portions, a first and a second dispersion compensators, each dispersion compensator having variable dispersion compensation to compensate chromatic dispersions of each of the two portions of signal light output from the optical divider, and a data demodulator to demodulate a data carried by a signal light output from the first dispersion compensator. The optical receiver further includes an optical autocorrelator to operate on a signal light output from the second dispersion compensator and a controller to control the second dispersion compensator to increase autocorrelation of the optical autocorrelator, and to control the first dispersion compensator according to the result of said controlling the second dispersion compensator.

Optical receiver and method for controlling dispersion compensation

To demultiplex a low-speed optical pulse signal from a high-speed optical pulse signal, an optical clock generator generates an optical clock of a control wavelength &#x3bb;p at a predetermined frequency out of a pulse signal light of a signal wavelength &#x3bb;s. On one side of a saturable absorber, an optical band reflection mirror is disposed to reflect a light of the signal wavelength &#x3bb;s and to transmit a light of the control wavelength &#x3bb;p. A pulse signal light of the signal wavelength &#x3bb;s reciprocates in the saturable absorber. An optical pulse of the pulse signal light of the signal wavelength &#x3bb;s enters the saturable absorber almost simultaneously with different optical pulses of the optical clock on the ways of going and returning. The saturable absorber has a transmission factor relative to the signal wavelength &#x3bb;s. The transmission factor varies as the saturable absorber absorbs a light of the control wavelength &#x3bb;p.

Optical pulse demultiplexer and method thereof

The present invention has an object to obtain an optical signal quality supervisory device that supervises the quality of an optical signal simply, efficiently and with high accuracy without inviting an increase in cost, an increase in circuit scale and increase in power consumption. The bit rate of the optical supervisory channel is made lower than the bit rate of the optical main channel that is transmitted over an optical communication system, but the reception electric band width of a receiver that receives the optical supervisory channel is made equal to or wider than the reception electric band width of a receiver that receives the optical main channel. Also, the optical supervisory channel is made up of an SOH (section over head) frame to detect an error of the BIP (bit interleaved parity) byte of SOH, thereby supervising the quality of the optical communication system, in particular, the light wave network.

Optical signal quality supervisory device

A four fiber ring network optical switching circuit capable of realizing the bridge function at times of the span switching and the ring switching economically by a very compact structure is disclosed. A four fiber ring network optical switching circuit is formed by a 10&times;8 optical matrix switch having ten input ports and eight output ports, and two branching elements adapted to branch each one of two optical signals among eight optical signals that are inputs of the four fiber ring network optical switching circuit, into two identical optical signals, and to enter the two identical optical signals into two input ports of the 10&times;8 optical matrix switch such that the eight optical signals are entered into the ten input ports of the 10&times;8 optical matrix switch as ten optical signals.

Four fiber ring network optical switching circuit using branched inputs

In a signal demultiplexing device formed by a probe light source, a wavelength converter, and a wavelength demultiplexer, the probe light source is formed by a plurality of sub-probe light sources configured to respectively generate the sub-probe lights with the prescribed different wavelengths for respective time-slots, a multiplexer configured to multiplex the sub-probe lights generated by the plurality of sub-probe light sources, and a phase different giving unit configured to give phase differences corresponding to time-slot positions to the sub-probe lights multiplexed by the multiplexer, and to sequentially output the sub-probe lights with the phase differences in correspondence to respective time-slots.

Signal demultiplexing device and signal routing device in high speed transmission system

An optical digital regenerator for digitally regenerating an input signal in an intact optical state. A first operating unit has a first probe light generator for generating a first probe light and a first optical operator for converting a waveform of the first probe light output from a first probe light generator according to an optical intensity waveform of the input signal light. A clock extractor extracts a clock component of the input signal light from a photocurrent generated by the first optical operator. A second optical operating unit has a second probe light generator for generating a second probe light pulsed in accordance with the clock output from the clock extractor and a second optical operator for sampling the second probe pulse light output from the second probe light generator.

Optical digital regenerator

An optical switching system is implemented by providing a transmitting section with a preparatory transmitted optical signal selector and a working transmitted optical signal splitter, which are each implemented by a 1&times;2 optical space switch, and by providing a receiving section with a receiving optical switch which is implemented by a 2&times;2 optical space switch, and with a preparatory receiving optical gate which is implemented by a 1&times;2 optical space switch. This makes it possible to switch between the working system and preparatory system without employing any 4&times;4 optical space switch, thereby implementing a practical optical switching system without causing such problems as communication interruption during maintenance or impairment of transmission path working efficiency.

Optical switching system

In a light source for generating light containing multiple wavelengths substantially uniform in intensity, a wavelength demultiplexing element,(for example, waveguide-type wavelength selecting filter) demultiplexes input light into a plurality of wavelengths &lgr;,through &lgr;,. Optical amplifiers,-,through,-,amplify outputs of the element,and applies them to input ports of a wavelength multiplexing element,. The wavelength multiplexing element,wavelength-multiplexes their input. Output of the wavelength multiplexing element,is applied to a fiber coupler,which, in turn, applies one of its outputs to the wavelength demultiplexing element,. The optical amplifiers,have a gain larger by approximately 10 dB than the loss in the optical loop made of the element,, optical amplifier,, element,and fiber coupler,. The other output of the fiber coupler,is wavelength-multiplex light containing wavelengths &lgr;,through &lgr;

Multi-wavelength light source and discrete-wavelength-variable light source

In an optical amplifier apparatus for amplifying an incident signal light having wavelengths of 1.06 &mgr;m band, a first optical isolator makes an incident signal light pass therethrough in one direction from an input end to an output end. An optical fiber includes a core mainly composed of silica glass and doped with a predetermined rare-earth element and the other elements, and a cladding of silica glass, and transfers in a single mode the signal light output from the first optical isolator. An optical multiplexer multiplexes an excitation light having an excitation wavelength of 0.8 &mgr;m band with the signal light transferred by the optical fiber, by outputting the excitation light to the optical fiber, and further transfers and outputs the signal light having wavelengths of 1.06 &mgr;m band amplified by induced emission in the optical fiber due to the rare-earth element excited by the excitation light. Further, a second optical isolator makes the signal light outputted from the optical multiplexer pass therethrough in one direction from an input end thereof to an output end thereof, and outputs the signal light as an amplified signal light.

1.06 &mgr;m band optical amplifier apparatus utilizing induced emission in optical fiber by excited rare-earth element

An optical wavelength routing device comprises an arrayed waveguide comprising a plurality of channel waveguides formed on a substrate, a plurality of input waveguides having 12 input ports located on an input side of the arrayed waveguide, a plurality of output waveguides having 16 input ports located on an output side of the arrayed waveguide, an input slab waveguide for coupling the plurality of input waveguides to the arrayed waveguide to provide a first coupling portion on the side of the input waveguide, and an output slab waveguide for coupling the arrayed waveguide to the plurality of output waveguides to provide a second coupling portion on the side of the output waveguide, in which central wavelengths of lights input to the input ports and output from the output ports are controlled such that a difference between a predetermined wavelength and a central wavelength is suppressed within the range of &plus;&dgr;&lgr;/4. By this structure, a maximum central wavelength difference can be suppressed at minimum.

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Tokyo, Japan

Tetsuya Miyazaki