Mitsubishi Electric Corporation

Mitsubishi Denki Kabushiki Kaisha

Kazuyuki Ishida

Katsuhiro Shimizu

Yukio Kobayashi

Takashi Mizuochi

Masahiro Ito

Takuya Ito

Yasushi Okoshi

Toshiyuki Tokura

Kosuke Tanaka

Tatsuya Kobayashi

Tsuyoshi Yoshida

Takashi Sugihara

Kuniaki Motoshima

Kenichi Nakura

Takeshi Suehiro

Satoshi Shirai

Takahito Hikone

Noriyuki Imada

Satoshi Kajiya

Yukio Hirano

Satoshi Yoshima

Hiromu Sato

Shunsuke Mitani

Kaoru Kinjo

Hideaki Ohashi

Ayano Sakamoto

Nanako Horayama

Yasushi Ookoshi

A single-fiber bidirectional optical ring system includes: a central station; slave stations; and a network which connects the central station and the slave stations in a ring shape by optical fibers. The central station includes: a first single-fiber bidirectional optical transceiver connected in a clockwise direction of the network, which outputs a downstream optical signal of a second wavelength and receives an upstream optical signal of a first wavelength; a second single-fiber bidirectional optical transceiver connected in a counterclockwise direction of the network, which outputs a downstream optical signal of the second wavelength and receives an upstream optical signal of the first wavelength; and a first time synchronization control circuit that adjusts timings at which the downstream optical signals of the second wavelength are outputted, and causes the first and second single-fiber bidirectional optical transceivers to output the downstream optical signals of the second wavelength in different time slots.

Single-fiber bidirectional optical ring system, method for controlling single-fiber bidirectional optical ring system, and central station

A refrigeration cycle apparatus is provided with a refrigerant circuit, a refrigerant tank circuit, and a degassing pipe. The refrigerant circuit is configured by connecting a compressor, a flow path switching apparatus, a first heat exchanger, a decompressing apparatus, and a second heat exchanger. The refrigerant tank circuit is connected to the first and second heat exchangers in parallel with the decompressing apparatus. The degassing pipe has a first end and a second end. The flow path switching apparatus is configured to switch a flow of refrigerant discharged from the compressor to any of the first and second heat exchangers. The refrigerant tank circuit contains a refrigerant tank. The degassing pipe has the first end connected to the refrigerant tank and has the second end connected to at least any of the refrigerant circuit and the refrigerant tank circuit.

Refrigeration cycle apparatus

A controller in a refrigeration cycle apparatus performs a refrigerant recovery operation when switching an operation mode from a defrosting mode to a heating mode. During the refrigerant recovery operation, by rotating a fan of a blower while monitoring a pressure at a discharge side of the compressor, the controller is configured to perform feedback control to cause a high-pressure side pressure to be close to a high-pressure side target pressure value. During the refrigerant recovery operation, by controlling a driving frequency of the compressor while monitoring a pressure at a suction side of the compressor, the controller is configured to perform feedback control to cause a low-pressure side pressure to be close to a low-pressure side target pressure value.

Refrigeration cycle apparatus capable of performing refrigerant recovery operation and controlling blower

In a refrigeration cycle apparatus, a controller is configured to, when a defrost mode is started, control a first pressure reducing device is controlled to adjust a flow rate of refrigerant to bring a degree of superheat of the refrigerant at a suction side of a compressor close to a target value, control a flow path switching device to form a first flow path through which the refrigerant released from the compressor flows to a first heat exchanger; perform a refrigerant release operation of opening one of a second pressure reducing device and a valve and closing the other of the second pressure reducing device and the valve, and perform a refrigerant collection operation of opening the second pressure reducing device and the valve, with the flow path switching device retained to form the first flow path, after the refrigerant release operation.

When multiplexed signal lights are amplified by optical amplifiers, a value of a monitor signal is compared with a threshold equivalent to a value of the monitor signal when noise indexes of the multiplexed signal lights start increasing. Next, when the value of the monitor signal is equal to or larger than the threshold, that is, when the powers of the multiplexed signal lights are large, a gain constant control is performed to amplify the multiplexed signal lights. Conversely, when the value of the monitor signal is smaller than the threshold, that is, when the powers of the multiplexed signal lights are small, an output constant control is performed to amplify the multiplexed signal lights.

Optical amplifier, wavelength multiplexing optical transmission system, and program

An optical communication system includes an optical-signal transmission unit transmitting an existing optical signal and a low-rate-signal superimposition unit superimposing a low-rate signal on the existing optical signal by intensity modulation. It further includes: a low-rate-signal extraction unit that extracts the low-rate signal from the existing optical signal on which the low-rate signal is superimposed and converts the extracted low-rate signal into a low-rate electric signal; an add-on optical-signal transmission unit that transmits an add-on optical signal; a low-rate-signal superimposition unit that superimposes a low-rate signal on the add-on optical signal by the intensity modulation based on the low-rate electric signal; and a repeater that repeats the add-on optical signal on which the low-rate signal is superimposed, to a transmission destination.

Optical communication system

In an optical transfer system, an optical transmission unit generates an optical signal in which respective polarization components are alternately present on a time axis, a time period during which the respective polarization components are simultaneously present on the time axis is substantially zero, and a symbol repetition cycle of optical signals of the respective polarization components becomes Ts, an optical reception unit causes an interference between local oscillation light and a received optical signal and converts an interfered optical signal to an electric signal, and a received electric-signal processing unit performs analog-digital conversion of an electric signal, elimination of a delay difference of Ts/2 between the respective polarized signal components, and adaptive equalization of a distortion other than the delay difference.

Optical transfer system, optical transmission device, and optical reception device

A control-target-value setting unit sets a control target value corresponding to the number of multiplexed wavelengths measured by a number-of-multiplexed-wavelengths measuring unit. A controller controls the variable optical attenuator based on the control target value. An optical amplifier performs an optical amplification with a constant gain regardless of power of a wavelength-multiplexed light. The controller performs feedback control of the variable optical attenuator such that a result of measurement of the total power of the wavelength-multiplexed light coincides with the control target value.

Optical relay device and optical relay transmission system

An optical reception device realizes stabilization of reception sensitivity inexpensively and highly precisely. The optical reception device includes: a Mach-Zehnder type 1-bit delay unit including a one-terminal input port and two-terminal output ports for decoding an optical difference phase shift keying (DPSK) signal and provided with one or more phase control functions to control the phase state of light; photoelectric conversion means for branching a portion of an optical output signal output from the one-side output port of the Mach-Zehnder type 1-bit delay unit, to convert the branched portion into an electric signal; and a phase control unit for controlling the phase state of the Mach-Zehnder type 1-bit delay device by using as an error signal the output signal of the photoelectric conversion means.

Optical reception device

A differential encoder generates a differentially encoded signal based on a data signal. An RZ (return to zero) encoder generates an electric RZ differential signal as an RZ signal in an electric area based on the differentially encoded signal. A Mach-Zehnder interferometer type intensity modulator generates an optical RZ-DSPK (differential phase shift keying) signal as an RZ signal in an optical area based on the electric RZ differential signal.

Optical transmitter

The optical transmission apparatus has a Mach-Zehnder optical modulator, a light source for applying an optical signal of a continuous light to the optical modulator, a driving circuit for inputting a driving signal into the optical modulator, a branching filter for taking out a part of an output optical signal, a photodiode for converting the taken-out output optical signal into an electric signal, a band pass filter for extracting a frequency component of a driving signal included in this electric signal, an error signal generator circuit for generating an error signal of a bias voltage that minimizes a value of the extracted frequency component, and a bias voltage control circuit for applying a bias voltage added with this error signal to the optical modulator.

Optical transmission apparatus and bias voltage control method for the optical modulator

In the multi-value modulation apparatus, one optical intensity detecting unit detects optical intensity of a modulation optical signal generated by one optical modulation signal generating unit and output from the variable optical attenuator. The detected optical intensity is provided to the comparator. Another optical intensity detecting unit detects optical intensity of a modulation optical signal output from another optical modulation signal generating unit. The attenuator attenuates the optical intensity detected by the another optical intensity detecting unit, and provides it to the comparator. The output of the comparator is provided to the optical variable attenuator as a control signal. The variable optical attenuator controls optical intensity of the modulation optical signal based on the control signal.

Multi-value modulation apparatus

The optical transmitter comprises a light source which inputs continuous optical signal and a driving circuit which inputs driving signal to an optical modulator of Mach-Zehnder type. A photo coupler separates a part of the output of the optical modulator. A photo diode converts this part into electric signal. A band-pass filter and a pre-amplifier extract a frequency component of the driving signal contained in the electric signal. A mixer conducts synchronous detection between the driving signal and the extracted frequency component. Finally, a bias voltage control circuit controls a bias voltage based on a result of the phase comparison.

Optical transmitter, and method of controlling bias voltage to the optical transmitter

An AWG (arrayed-waveguide grating/ A) divides input ports ( A to A ) into 1 number of groups, each group comprising m number of input ports, and combines optical signals belonging to each of the groups. For example, the optical signals of wavelengths &lgr; to &lgr; are input from the input ports ( A to A ) and output from an output port ( A ) as multiplex light. The multiplex light output in each of the groups in the above manner is input into a wave combination coupler ( A) and output to a transmission line ( A) as multiplex light of the optical signals of the wavelengths &lgr; to &lgr; .

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Tokyo, Japan

Kazuyuki Ishida