Fujitsu Corporation

Riken Corporation

Tomohiro Ueno

Masaji Noguchi

Yutaka Kai

Setsuo Yoshida

Hideyuki Miyata

Goji Nakagawa

Masashige Kawarai

Koichi Sugama

Takashi Kaiga

Yukio Katayanagi

Hiroyuki Ishii

Hiroshi Onaka

Kenichi Hasegawa

Yasuhiko Aoki

Kyosuke Sone

Hiroyasu Ito

Junichi Sugiyama

Toshihisa Kyouno

Katsuya Tsushita

Yuichi Nagaki

Hiromitsu Yanaka

Kentaro Sano

A first node and a second node transmit packets to a third node via a switch. The packets are buffered in a Tx buffer in the switch and then transmitted to the third node. When the third node detects a sign of congestion at the Tx buffer based on the reception frequency of the packets, it is recognized, from transmitter addresses included in the received packets, that the nodes transmitting the packets to the third node are the first node and the second node, and a control packet for a transmission stop request is transmitted to the first node and the second node. On receiving the control packet for a transmission stop request, the first node stops transmission of only packets addressed to the third node. On receiving the control packet for a transmission stop request, the second node stops transmission of only packets addressed to the third node.

Communication apparatus and communication method

A transmission apparatus includes a network-side interface unit configured to receive a signal transmission frame into which a client signal is arranged from each of a working line and a protection line of a network, and extract the client signal from the received signal transmission frame, a client-side interface unit configured to transmit the extracted client signal to a client transmission path by using a generated clock, based on frequency adjustment information of the client signal included in the signal transmission frame, a protection-line-side memory configured to store the frequency adjustment information of the client signal included in the signal transmission frame received from the protection line, and a switch controller configured to control to generate a clock by using the frequency adjustment information of the client signal stored in the protection-line-side memory when the signal transmission frame fails to be received from the working line.

Transmission apparatus and transmission method

A transmission device includes a receiver receiving a signal transmission frame from a network, where a client signal is mapped to the signal transmission frame; a separator separating the client signal from the signal transmission frame; a phase synchronizer generating a clock based on a frequency adjustment information set of the client information included in the signal transmission frame; a transmitter transmitting the client signal to a client transmission path by using the clock generated by the phase synchronizer; a memory storing the frequency adjustment information set included in the signal transmission frame in response to receiving the signal transmission frame from the network by the receiver; and a switch controller causing the phase synchronizer to generate a clock based on the frequency adjustment information set stored in the memory in response to not receiving the signal transmission frame from the network by the receiver.

Transmission device and transmission method

A driving circuit of a semiconductor optical amplifier type gate switch constituting a matrix optical switch is provided with an operation amplifier into which a driving signal is input and from which a current corresponding to the driving signal is output, an inductance element provided at an output terminal of the operation amplifier, and a circuit composed of a diode element and a resistor element connected in parallel and provided between the inductance element and the semiconductor optical amplifier.

Driving circuit of optical gate switch

A non-inverting amplifier circuit is disclosed that includes an operational amplifier and a preemphasis circuit connected between the operational amplifier and a signal source. The preemphasis circuit is configured to compensate for the internal delay of a load connected to the output of the operational amplifier by emphasizing a high-frequency component of a signal fed from the signal source.

Non-inverting amplifier circuit and optical switch driver circuit

A drive circuit is provided for a semiconductor optical amplifier type gate switch includes a first transmission path and a second transmission path. The first transmission path includes a common first sub-path between a signal source and a first node; and an individual second sub-path for each of a plurality of operational amplifiers between the first node and a corresponding one of the operational amplifiers. The second transmission path includes an individual third sub-path between each of the operational amplifiers and a second node; and a common fourth sub-path between the second node and the semiconductor optical amplifier type gate switches. Transmission delay times of all the individual second sub-paths are equal, and transmission delay times of all the individual third sub-paths are equal.

Semiconductor optical amplifier gate switch drive circuit, semiconductor optical amplifier gate switching device, and optical cross connect

An optical communication apparatus for controlling the operating point of an optical modulation unit appropriately. An adding unit adds a bias voltage and a pilot signal. An optical modulation unit modulates light by an electrical signal, performs further modulation by a signal from the adding unit, and outputs an optical signal. A monitor unit monitors the level of the optical signal and outputs a monitor signal. A reference signal output unit outputs a reference in phase with the pilot signal contained in the monitor signal. A synchronous pilot-signal detection unit performs synchronous detection of the monitor signal by using the reference. A synchronous noise detection unit extracts noise from the monitor signal and performs synchronous detection of the noise by using the reference. A control signal output unit subtracts the synchronous detection value of the noise from that of the monitor signal, and outputs a control signal.

Optical communication apparatus

An AOTF control apparatus, which applies an RF signal to an AOTF to allow a selected light to pass through the AOTF, includes: a first calculating unit calculating a relationship between a frequency of the RF signal and a wavelength of the selected light based on a frequency of the RF signal that allows a reference light to pass through the AOTF; and a second calculating unit calculating a relationship between a power of the RF signal and an attenuation amount of the selected light based on an input/output power of the reference signal at the input/output of the AOTF.

Acousto-optic tunable filter control apparatus automatically adjusting frequency and power of radio frequency signal

An optical transmission device improved in quality and reliability of OADM function and permitting configuration of highly-flexible, economical OADM networks. A wavelength tunable filter variably selects a wavelength according to a control frequency. A filter controller applies the control frequency to the filter while scanning wavelength over an entire signal bandwidth, to detect, from a reference wavelength monitor signal supplied thereto, a reference control frequency which permits the filter to select a reference wavelength and according to which wavelength is matched. On receiving a wavelength selection request, the controller obtains a target control frequency from the reference control frequency and the position of a target wavelength relative to the reference wavelength, and applies the obtained frequency to the filter. A reference wavelength filter transmits the reference wavelength therethrough. A light-receiving element monitors the transmitted reference wavelength to generate the monitor signal.

Optical transmission device

A method of wavelength selection control is disclosed. The method includes detecting reference RF frequencies by varying the frequency of a RF signal supplied to a reference acousto-optic tunable filter with the reference RF frequencies corresponding to reference wavelengths of reference signals input to the tunable filter, performing tracking to optimize the reference RF frequencies, calculating dependent RF frequencies corresponding to wavelengths of WDM transmission signals and recording the calculated dependent RF frequencies in a first register, repeating the above when a request of wavelength selection is not received, when a request of wavelength selection is received, selecting one of the dependent RF frequencies corresponding to the requested wavelength and recording the selected dependent RF frequency in a second register for use of an acousto-optic tunable filter at a port in operation, and generating and supplying a RF signal having the selected dependent RF frequency to the acousto-optic tunable filter.

Method of wavelength selection control and wavelength variable filter device

A radio-frequency-signal generator generates an RF signal. An optical monitor monitors a first intensity of a reference signal and a second intensity of a drop signal. A reference-frequency determining unit determines, based on the first intensity, a first frequency of an RF signal that causes the AOTF to output the reference signal. A temperature detecting unit detects a temperature of the AOTF. A frequency calculating unit calculates a second frequency of an RF signal that causes the AOTF to output a drop signal of a desired wavelength. A control unit controls the RF-signal generator to generate the RF signal of the second frequency calculated.

Growing community of inventors

Kawasaki, Japan

Tomohiro Ueno