Nippon Telegraph and Telephone Corporation

Kana Masumoto

Toshiya Matsuda

Masahiro Nakagawa

Hidetoshi Onda

Kazuyuki Matsumura

Masaru Katayama

Toru Homemoto

Katsutoshi Koda

A relay device (bA) includes an optical signal return unit () and a detection unit (). When an optical signal input via one optical transmission line () of two optical transmission lines (and) with a double-ring configuration has not been detected for a predetermined time or longer, the detection unit () outputs a disconnection signal of the optical transmission line. The optical signal return unit () is configured to, only when there is an input of the disconnection signal, return to one of the optical transmission lines () only a clamp beam that has been sent from a representative node via the other optical transmission line () in the direction opposite to the optical signal input via the one of the optical transmission lines ().

Burst optical relaying device and burst optical relaying method

A server that performs optical transmission using an optical transmission line includes a transmitter that transmits an optical signal to another server, a receiver that receives the optical signal from the other server, a storage device that stores data and an error correction code (ECC) added to the data, and a control unit that controls conversion of the data and the ECC into the optical signal, conversion of the optical signal into the data and the ECC, and error correction of the data using the ECC, and a transmission distance of the optical transmission line is a transmission distance for which an error rate does not exceed an allowable value of the error rate before correction which makes the error rate after correction based on the error correction using the ECC be equal to or less than a reference error rate.

Server, optical transmission method, optical transmission system, and optical transmission program

Device cost and electric power consumption are reduced. Nodestoas optical add/drop multiplexers each include AWGsandconnected between light transmission paths as optical fibersandand transponderstoand configured to output optical signals from the light transmission paths to the transponderstothrough ports and transmit optical signals from the transponderstoto the light transmission paths through ports, and an optical couplerconfigured to connect ports of the AWGsandto the transponderstothrough coupling or bifurcation. The channel interval of ports of the AWGsandis multiple times larger than the channel interval of ports of the transpondersto, and transponder signals of a plurality of different wavelengths to and from one or a plurality of the transponderstocan pass through ports of the AWGsand

Optical branch insertion device and optical transmission system using optical branch insertion device

Device cost and electric power consumption are reduced. Nodestoas optical add/drop multiplexers each include cAWGsandthat include a plurality of first side ports and a plurality of second side ports connected between light transmission paths as optical fibersandand transponderstoand in which a first optical signal input-output channel interval of each port is a plurality of times larger than a second optical signal input-output channel interval of ports of the transponderstoand optical signals of a plurality of different wavelengths from one or a plurality of transponderstoor the light transmission paths can pass through a first channel. The cAWGsandcause the optical signals from the transponderstoto pass through the first side ports, and then cyclically outputs and transmits the optical signals through the plurality of second side ports in a predetermined order to the light transmission paths. The optical signals transmitted through the light transmission paths are caused to pass through the second side ports and then output from the plurality of first side ports in a predetermined order to the transpondersto

[Problem] An optical receiver using a polarization demultiplexing technique is miniaturized. [Solution] An optical receiverA for receiving a polarization multiplexed signal obtained by performing orthogonal polarization multiplexing on two optical signals. The optical receiver includes an ILsplitting the polarization multiplexed signal into two transmitted signals that are asymmetric in terms of a light transmission characteristic, O/Esandconverting the transmitted signals resulting from the split into electrical signals, a downsamplerdownsampling the electrical signals resulting from the conversion to generate low-speed digital signals, a calculatorcalculating coefficients of a polarization separation matrix from the resultant low-speed digital signals, a level adjusterA adjusting, in accordance with the coefficients resulting from the calculation, signal levels of the electrical signals resulting from the conversion to generate a plurality of adjustment signals, addersAa andAb adding the generated adjustment signals to generate addition signals, and discriminatorsandrestoring and extracting the two optical signals from the generated addition signals.

Optical receiver

An optical demultiplexerincludes: a plurality of optical gate switchestoconfigured to transmit, when being turned on, and to block, when being turned off, a multiplexed optical signal obtained by multiplexing optical signals of a plurality of wavelengths by time-division multiplexing or wavelength-division multiplexing in addition to time-division multiplexing; and a cAWGincluding a plurality of input ports and a plurality of output ports and configured to input the multiplexed optical signal transmitted through the optical gate switchestofrom the plurality of input ports, demultiplex the input multiplexed optical signal for each wavelength, and cycle and output the demultiplexed optical signals from the plurality of output ports in a predetermined order.

Optical demultiplexer, optical separation device, optical transmission system, and optical transmission method

A function of detecting an unused path through which actual data is not transmitted in a long-distance redundant network is realized at low cost. In an optical transmission system, each of the optical transceiversandthat are connected to each other by an optical fiber cableand disposed separately includes a protocol IC unit. The protocol IC unittransmits an idle signal Awith empty data using an optical signal Pto an unused path of the optical fiber cable. At the time of this transmission, the protocol IC unitoutputs, to the transmission unit, a control signal Cfor performing, at a fixed modulation period, ON/OFF modulation on the optical signal Pon which the idle signal Ais superimposed. Also, the protocol IC unittransmits an OAM signal Oat an OAM period that is a period different from a modulation period, and performs control to turn ON the control signal Cat the time of this transmission. The protocol IC unitperforms control to set the QAM period Tas a period longer than or equal to a plurality of modulation periods T. The transmission unitis configured to perform ON/OFF modulation on the optical signal Pusing the control signal C, and transmits the modulated optical signal P

Optical transmission system and unused channel verification method

An unused path through which actual data is not transmitted in a long-distance redundant network can be appropriately detect, and this function is realized at low cost. A transmission unitof optical transceiversandconnected to each other by an optical fiber cablein an optical transmission systemincludes a laserfor emitting a laser beam serving as an optical signal Pto the optical fiber cable, and an optical intensity control unitfor performing control to change the optical level of the optical signal of the laser beam. Each of the optical transceiversandincludes a control unitfor superimposing each of an idle signal A, an OAM signal O, and an actual data signal Don an XGMII signaland outputting this XGMII signalto the transmission unitthat transmits the optical signal P, and a signal determination unitfor determining unique information regarding each signal output to the transmission unitand outputting a determination result signal. The optical intensity control unitperforms control to change the optical level of the optical signal Pon which a signal of the determination of each signal indicated by the determination result signalis superimposed to different optical levels Lto Lbetween the signals.

An object is to provide a dispersion compensating system with a large amount of dispersion compensation and reduced operation costs. Disclosed is a dispersion compensating system in which a core node and an access node are connected through a ring network, the access node includes a delay measurement unit configured to receive delay measurement signals from the core node to measure a delay between the core node and the access node, an average dispersion amount calculation unit configured to calculate an amount of dispersion compensation to be applied to an optical burst signal prior to transmission to the ring network, based on the delay thus measured, and a real-part inverse dispersion application unit configured to perform pre-equalization on a waveform of the optical burst signal prior to the transmission, based on the calculated amount of dispersion compensation.

Dispersion compensation system and dispersion compensation method

[Problem] To allow addition of new functions to an optical module at a low cost. [Solution] An optical transceiverincludes a CPUconfigured to perform download control of a program for executing an additional function to be newly added to the optical transceiver, a wireless transmitting and receiving deviceconfigured to receive, in accordance with the download control, the program from a terminal devicethat stores various programs, and a memory unitconfigured to store the program that is received. The CPUis configured to perform, by interrupting a monitoring and control signal from a transmission device, control to write data related to transmission and reception processing of a Txand a Rxin accordance with execution of the programs stored in the memory unitin a storage area at a specific address of an EEPROM

Optical transceiver

An optical transmitter generates two modulated optical signals by modulating two optical carriers respectively with two binary bit sequences by on-off keying and generates an orthogonal polarization multiplexed optical signal from the two modulated optical signals. The two optical carriers respectively have peak frequency components spaced apart from each other by a predetermined frequency difference and located such that a central frequency of a WDM channel of a WDM grid falls between the peak frequency components. An optical receiver separates the orthogonal polarization multiplexed optical signal into two signals in which components of the two modulated optical signals are combined with different combination ratios, by means of a 1-input, 2-output asymmetric filter whose two optical transmittances intersect at the WDM grid and each have a free spectral range equal to or twice the channel spacing of the WDM grid, and restores the two modulated optical signals from the separated two signals using a DSP.

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Tokyo, Japan

Kana Masumoto