Abstract: A ring connection apparatus according to one embodiment is provided with: a frame receiver that receives frames to be transmitted to one of the plurality of ring networks from each of the plurality of networks; and a frame transmitter that transmits each of frames, a passing frame to be transmitted from a device to another device inside said one ring network and a crossing frame to be transmitted to a device in said one ring network from a device in another ring network different from said one ring network, to said one ring network within the range of a band, which is separately determined in advance.

Abstract: A client interface unit receives a pause frame transmitted from a client device compatible with a relatively low communication rate. A data rate conversion unit generates a plurality of pause frames in accordance with a pause time designated by the received one pause frame and transmits the plurality of pause frames to a frame processing unit compatible with a relatively high communication rate. The frame processing unit stops transmitting a frame destined to the client device in accordance with the plurality of pause frames.

Abstract: An optical packet switching system includes a plurality of network elements for transmitting and receiving optical packet signals. Each network element includes an optical signal-to-noise ratio (OSNR) acquiring unit for acquiring the OSNR of each optical packet signal, an average value calculating unit for calculating the average value of the OSNRs of optical packet signals received within a predetermined time duration for each of the plurality of source network elements, and a difference information transmitter for calculating the difference between the calculated average value of the OSNRs and a target value of the OSNRs and then transmitting the difference to a network element corresponding to the difference. A source network element that has received the difference information adjusts the characteristics of an optical packet signal to be transmitted in a manner such that the difference is reduced.

Abstract: A frame transmission apparatus includes multiple ports provided in a line unit, and a setting control unit. The setting control unit checks the normality of the frame transfer state within the apparatus by transferring a maintenance management frame from a first port to a second port within the apparatus. When the first port is a logical port configured by link aggregation of multiple physical ports, the setting control unit selects each of the multiple physical ports as a transmission source port and transfers multiple maintenance management frames from the multiple physical ports to the second port.

Abstract: A communication system includes a plurality of communication devices forming a ring network and a monitoring device. Each of the plurality of communication devices appends, to a frame that the communication device relays, an ID tag indicating the number of communication devices relaying that frame in the ring network. The monitoring device refers to frames received by a predetermined communication device and having the ID appended thereto, and tallies an amount of data for frames for each number of relaying communication devices.

Abstract: A plurality of frame buffers of a communication device store input frames for respective flows, which are units of managing communication. A sequential scheduler and an adjustment scheduler cyclically visit the plurality of frame buffers to read a frame for external output from each frame buffer. The sequential scheduler reads one frame per a visit to each frame buffer at a speed lower than a communication speed of the communication device. The adjustment scheduler reads one or more frames per a visit to each frame buffer such that a restriction on read quantity defined by a reference value greater than the shortest frame size is imposed.

Abstract: A communication apparatus forming a ring network sends a test frame that is not designed to be discarded at a block point in the ring network established to discard the user frame and that is configured to have a data size randomly selected from the data sizes permitted for the user frame, from a first communication port connected to a transfer channel in a first direction in the ring network. The communication apparatus determines that the transfer status of the user frame in the ring network is normal when the sent test frame is received via a second communication port connected to a transfer channel in a second direction in the ring network in a predetermined manner.

Abstract: An excitation light source, for Raman amplification, includes a polarization beam splitter (PBS) for splitting a laser beam from an excitation laser into two polarization components, and a polarization beam combiner (PBC) for combining the two polarization components, and a time difference generator provided between PBS and PBC. The time difference generator generates a difference in propagation time between the two polarization components.

Abstract: An optical receiving device includes: an optical amplifier configured to amplify a wavelength multiplexed optical signal; a demultiplexer configured to demultiplex the amplified wavelength multiplexed signal into optical signals of a plurality of wavelengths; optical receivers configured to regenerate the demultiplexed optical signals; error correction units configured to correct a bit error in the regenerated optical signals; and main control unit. The control unit adjusts RXDTV of the optical receiver for receiving optical signals of a given wavelength to the optimal value in the state where the gain of the optical amplifier is lowered from that of a normal operation such that the occurrence of bit errors in the optical signals of the other wavelengths does not exceed the correction capability of the error correction unit.

Abstract: An optical packet switching apparatus includes an optical packet switching apparatus, an optical transmitting apparatus, and an optical packet receiving apparatus. The optical packet transmitting apparatus includes a packet generator for generating a packet signal by adding the routing information to a received client signal, a BIP adding unit for adding BIP to the generated packet signal, and an electrical-to-optical converter for converting the packet signal, to which the BIP has been added, into an optical packet signal so as to be sent out. The optical packet receiving apparatus includes an electrical-to-optical converter for converting the received optical packet signal into an electrical packet signal, and a BIP comparison unit for detecting the error occurrence in the packet signal, based on the BIP added to the packet signal.

Abstract: An optical receiving apparatus includes a variable dispersion compensation unit, a delay interference unit, a photoelectric converter, a polarization control unit for control the polarization state of an optical signal inputted to the photoelectric converter, a received data processing unit for monitoring the number of error occurrences, and a control unit for controlling the dispersion compensation amount at the variable dispersion compensation unit and the optical phase control amount at the delay interference unit, based on information on the number of error occurrences from the received data processing unit.

Abstract: An optical packet switching device causes branching of an optical packet that is input to an optical switch and detects a synchronization pattern having a predetermined number of bits from the branched optical packet. Then, the optical packet switching device calculates a synchronization point indicating a location of the synchronization pattern with respect to a detection timing and controls, in accordance with the calculated synchronization point, a delay amount of a delay element that delays an optical packet ON signal that is output to the optical switch.

Abstract: An optical packet switching device is provided with: a first input unit and a second input unit for receiving optical packet signals having destination information and information of a wavelength in use; an optical switch unit for routing the optical packet signals; a branching unit for branching the received optical packet signals; an analyzer unit for analyzing the header of the branched optical packet signals so as to detect the destination information and the information of the wavelength in use; and an output competition determination unit for checking for temporal competition of the optical packet signals based on the destination information and for determining whether the optical packet signals should be transmitted or discarded based on the information of the wavelength in use when there is competition.

Abstract: An optical packet transmitter device includes: a detection unit for detecting packet-length information and priority information from a received Ether signal; a setting unit for setting, according to the degree of priority, a division factor by which the Ether signal is divided and a wavelength used for an optical packet signal to be transmitted; a header generation unit for generating a header containing destination information, the packet-length information, the priority information, and information of wavelength in use of the Ether signal; a transmission processing unit for dividing the Ether signal according to the set division factor and generating a plurality of packet signals; a header insertion unit for inserting the generated header in at least one packet signal; and an electrical/optical converter unit for converting the plurality of packet signals into optical packet signals of a plurality of wavelengths according to the set wavelength in use.

Abstract: Raman amplifier includes: a pump-light generator configured to supply pump light to a transmission fiber; a measurement circuit configured to measure a relationship between power of the pump light and power of noise output from the transmission fiber with respect to a range from first pump-light power to second pump-light power; a signal detector configured to monitor a supervisory signal in output light of the transmission optical; and a decision unit configured to decide a state of the transmission fiber according to the monitoring result. When the supervisory signal is detected without the pump light, the measurement circuit measures the relationship while increasing the power of the pump light from the first pump-light power. When the supervisory signal is not detected without the pump light, the measurement circuit measures the relationship while decreasing the power of the pump light from the second pump-light power.

Abstract: An optical packet switching device is provided with: a first input unit and a second input unit for receiving an optical packet signal having destination information and priority information; a first demultiplexer and a second demultiplexer for branching the optical packet signal; an optical switch unit for routing one of branched optical packet signals; a first analyzer unit and a second analyzer unit for analyzing the header of the other branched optical packet signal so as to detect the destination information and the priority information; and an output competition determination unit for checking for temporal competition of a plurality of optical packet signals based on destination information and for determining whether the optical packet signals should be transmitted or discarded based on priority information when there is competition.

Abstract: An optical transmission system includes a polarization multiplexing optical transmitter for transmitting an optical signal, where an X-polarized signal and a Y-polarized signal each having a having predetermined frame structure are polarization-multiplexed, to an optical fiber transmission path, and a polarization multiplexing receiver for receiving the optical signal that has propagated through the optical transmission path. The polarization multiplexing optical transmitter delays a frame assignment signal (FAS) in the Y-polarized signal, by a predetermined delay time ?, relative to FAS in the X-polarized signal.

Abstract: An optical packet switching system includes: an optical packet switching device configured to route and output an input optical packet signal; an optical amplifier device provided in a stage subsequent to the optical packet switching device; and a control signal generation unit configured to superimpose a noise component on the optical packet signal by inducing cross talk in the optical packet switch.

Abstract: An optical packet switching system includes an optical packet generator for generating an optical packet signal, an optical packet switching unit, provided with an optical switch, for switching the route of an inputted optical packet signal by controlling on/off of the optical switch, and an optical signal-to-noise ratio measuring unit for measuring the optical signal-to-noise ratio of the optical packet signal outputted from the optical packet switching unit. When switching the route of the optical packet signal, the optical packet switching unit outputs an optical packet signal with optical noise by keeping the optical switch on longer than the time width of the packet signal. The optical signal-to-noise ratio measuring unit measures the optical signal power and the optical noise power, respectively, in the optical packet signal with optical noise and measures the optical signal-to-noise ratio by calculating the ratio between the optical signal power and the optical noise power.

Abstract: A communication apparatus of the embodiment is provided with a first IF card that performs a relay process of a data frame in a first direction of a ring network, a second IF card that performs a relay process of a data frame in a second direction of the ring network, a communication-status determination unit that monitors the communication status from the first IF card to the second IF card, a block control unit that sets a new block point to either the first IF card or the second IF card when the communication status is abnormal, and a ring protocol processor that notifies other communication apparatuses that constitute the ring network of information for notifying the switching of a block point in the ring network, which indicates that the new block point has been set.