Fujitsu Corporation

Fujitsu Optical Components Limited

Kiyotoshi Noheji

Miki Onaka

Masanori Kondoh

Togo Fukushi

Yasushi Sugaya

Hiroki Ooi

Akira Miura

Masato Nishihara

Noriaki Mizuguchi

Takashi Hayasaka

Takuya Miyashita

Makoto Murakami

Haruka Shinohara

Eisuke Nakamura

An optical transmitter includes: a light source; a wavelength detecting unit configured to detect a wavelength of light emitted from the light source; a wavelength difference information generating unit configured to generate wavelength difference information representing a wavelength difference between a predetermined reference wavelength and a wavelength of the light detected by the wavelength detecting unit; a subcarrier count determination unit configured to determine a number of subcarriers to be used, based on the wavelength difference indicated by the wavelength difference information; a multi-valued level determination unit configured to determine, for each of the subcarriers, a multi-valued level which is a number of bits transmitted by a corresponding subcarrier of the subcarriers; a modulated signal generating unit configured to generate a modulated signal by modulating the subcarriers such that each of the subcarriers has the determined multi-valued level.

Optical transmitter and optical transmitting method

A determination device for a wavelength division multiplex communication system, configured to set each of different paths each of which is formed by connection of spans each of which is a zone between two adjacent transmission devices, among transmission devices forming a communication network, in the communication network, or a single span in the communication network, for the corresponding one of different wavelengths, and configured to transmit an optical signal of each of the wavelengths via the corresponding path set to the wavelength, the device includes: a determination section configured to determine whether an optical signal of at least one of the wavelengths is transmittable only to a path, among newly formed paths, for which the number of spans forming the path is equal to or less than a predetermined upper-limit number, in order to transmit one or more optical signals of one or more wavelengths among the wavelengths.

Determination device and determination method

A digital coherent optical receiver executing coherent reception of a phase-modulated optical signal, includes: a moving average section configured to execute a moving average for received data obtained by sampling of the phase-modulated optical signal; a compensator configured to compensate a wavelength dispersion value of the phase data having been executed with the moving average; and a control section configured to determine a moving average frequency to be executed by the moving average section based on the compensated wavelength dispersion value.

Digital coherent optical receiver, control method of the same, and transmission apparatus

A characteristic compensation method includes obtaining compensation information when degradation of a transmission characteristic of an optical transmission path of a received light signal is compensated for by using digital signal processing with respect to an electric signal obtained by photoelectrically converting the light signal, calculating an compensation value for a characteristic compensation device that optically compensates for degradation of the transmission characteristic to start characteristic compensation, based on the compensation information with respect to the light signal, setting the compensation value in the characteristic compensation device, and switching a state in which compensation is done using the digital signal processing to a state in which compensation is done using the characteristic compensation device after the setting of the compensation value is completed.

Optical transmission apparatus and characteristic compensation method

An optical receiver includes a dispersion mitigator configured to mitigate a wavelength dispersion value in an optical signal by using a set dispersion value, a phase difference signal generator configured to generate a phase difference signal by calculating the phase difference between a first clock signal included in an optical signal mitigated by the dispersion mitigator, and a second clock signal, a dispersion value adjuster configured to adjust the set dispersion value set in the mitigator, a controller configured to control fluctuations appearing in a phase difference signal generated by the phase difference signal generator when the dispersion value is adjusted by the dispersion value adjuster, and a clock generator configured to generate the second clock follow up the phase of the first clock, being based on the phase difference signal controlled by the controller.

Optical receiver and clock generation method

In a dispersion compensating apparatus, a reference identifying unit identifies a reference (X dB down) that makes a penalty lower than a predetermined value in accordance with optical signal information and a reference identifying table, and a VIPA plate temperature adjusting unit adjusts a refractive index of a VIPA plate by modifying a temperature of the VIPA plate so that a transmission center wavelength derived from the reference matches the wavelength defined by an ITU-T Grid. If a dispersion compensation value setting unit performs an optimal residual dispersion value search, the VIPA plate temperature adjusting unit determines if a filtering penalty is lower than a predetermined value in accordance with a penalty management table. If the filtering penalty is lower than the predetermined value, temperature adjustment of the VIPA plate is not performed.

Dispersion compensating apparatus and dispersion compensating method

To obtain automatic gain control with high accuracy by including first and second light monitors, a reference light supplying unit supplying reference light of which wavelength is set within a gain band of a distributed Raman amplification and out of a wavelength band of main signal light to the optical transmission path, a first reference light monitor monitoring a power of the reference light input to the optical transmission path from one end side thereof, a second reference light monitor monitoring the power of the reference light output from the other end side of the optical transmission path, and a controlling unit controlling supply of pump light in a pump light supplying unit as well as supervising a state of the optical transmission path, based on monitor results from the first and second light monitor and the monitor results in the first and second reference light monitors.

Distributed Raman amplifying system, start-up method thereof, and optical device

A light amplifying device including a Raman amplifier to Raman-amplify a signal light by inputting excitation lights of a plurality of wavelengths to a transmission path through which the signal light propagates, a plurality of measuring units measuring powers of light output from the Raman amplifier in a plurality of wavelength bands included in an amplification band of the Raman amplifier, a calculating unit calculating a ratio of the respective powers measured by at least two of the plurality of measuring units, and a control unit controlling a power ratio of the respective excitation lights input to the transmission path by the Raman amplifier based on the ratio calculated by the calculating unit.

Raman amplifying device and control method

A Raman amplification apparatus includes a pumping light supplying section, a main signal wavelength light level acquisition section, a monitoring signal wavelength light level acquisition section, a function information storage section for storing, as function information, information regarding functions for deriving a noise amount and a gain by Raman amplification with regard to a monitoring signal wavelength light with respect to pumping light power supplied from the pumping light supplying section, and a transmission characteristic derivation section for deriving a transmission characteristic on an optical transmission line based on information acquired by the main signal wavelength light level acquisition section and the monitoring signal wavelength light level acquisition section and the function information stored in the function information storage section, and Raman gain is derived with high accuracy in comparison with the conventional technique.

Raman amplification apparatus and distributed raman amplification system as well as starting up method for distributed raman amplification system

A Raman amplifier inputs pump light into an optical fiber (transmission path) through which an optical signal passes, to amplify the optical signal. An optical receiving unit is provided downstream of the Raman amplifier and monitors the power of the optical signal amplified by the Raman amplifier. A calculating unit determines Raman amplification gain based on the power of the optical signal monitored by the optical receiving unit, and calculates the power of a noise component included in the optical signal based on the gain. The calculating unit, in real-time, calculates the power, which varies in complicated manners depending on conditions, and outputs information concerning to the power to another apparatus at a frequency on the order of milliseconds.

Optical amplification apparatus, optical communication apparatus, and optical communication method

The WDM optical transmission system using distributed Raman amplification, before starting operation of main signal light, transfers a plurality of lights having different wavelengths to that of the main signal light (for example Raman amplification pump lights or the like) between first and second optical transmission devices connected to opposite ends of a transmission line, monitors transmission line input and output power for each light, calculates a transmission line loss in each wavelength using the monitor results, and specifies a type of the transmission line based on a loss wavelength characteristic that can be estimated from the calculation result. Then the power of pump light provided to the transmission light is optimized in accordance with the type of transmission line.

Wavelength division multiplexing optical transmission system utilizing distributed raman amplification

An optical reception apparatus according to the present invention comprises: a branching section that branches an optical signal input thereto into two; first and second delay interferometers arranged on optical paths through which the branched lights are propagated; first and second photoelectric converting sections that receive the output lights from the delay interferometers; a clock recovery circuit for recovering a clock signal based on a data signal output from one of the photoelectric converting sections; a multiplexing section that multiplexes data signals from the photoelectric converting sections in accordance with the clock signal; and a delay interferometer control section that resets operating conditions of the delay interferometers when the frame synchronization is not achieved. Thus, it becomes possible to perform the demodulation processing on the signal light which is differential phase shift keying modulated using a quadrature phase component, utilizing a general-purpose framer.

Optical reception apparatus

In order to enhance dispersion control, the apparatus includes a dispersion controller; a quality index generator generating a quality index representing a quality of an optical signal output from the dispersion controller; and a searching unit searching for an amount of dispersion control applying to the dispersion controller which amount optimizes the quality index, wherein the searching unit includes a splitting-half searching unit roughly searching, in a splitting half method, a range in which dispersion is controllable by the dispersion controller for an amount of dispersion control such that the quality index generated by the quality index generator becomes preferable, and a sweep searching unit thoroughly searching, by sweeping, a limited range based on the amount of dispersion searched by the splitting-half searching unit for an amount of dispersion control that optimizes the quality index generated by the quality index generator.

Dispersion compensation controlling apparatus and method for searching for amount of dispersion control

Disclosed herein is a system including a closed loop topology using an optical fiber applicable to WDM signal light obtained by wavelength division multiplexing a plurality of optical signals, and a plurality of nodes arranged along the closed loop topology, each node including an optical amplifier. Each node further includes a first unit for controlling the optical amplifier so that the output from the optical amplifier becomes constant, according to the number of channels of WDM signal light received from the node immediately upstream of the corresponding node, and a second unit for interrupting the optical signals other than one or more optical signals added to the corresponding node until the control by the first unit is converged. With this configuration, each node can be easily started.

Optical transmission system

An optical transmission apparatus that improves optical transmission quality by performing an optical noise correction and optical level detection with great precision. A first optical amplifier performs optical amplification with an optical fiber transmission line as an amplification medium. A second optical amplifier inputs second excitation light into an amplification medium in which an active substance for optical amplification is doped to perform optical amplification. A first optical level detector monitors, before transmitting an optical signal, a level of optical noise scattered by the first optical amplifier by emitting first excitation light in an operating environment and detects an optical level at the time of transmitting the optical signal by subtracting the level of the optical noise from a signal amplified by the first optical amplifier. A second optical level detector monitors, before transmitting an optical signal, a level of optical noise emitted from the second optical amplifier by emitting the second excitation light in the operating environment and detects an optical level at the time of transmitting the optical signal by subtracting the level of the optical noise from a signal amplified by the second optical amplifier.

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Kawasaki, Japan

Kiyotoshi Noheji