Nippon Telegraph and Telephone Corporation

Ntt Electronics Corporation

Deutschetelekom Ag

Nippon Telegraph and Telephone Coproration

Yutaka Miyamoto

Takayuki Kobayashi

Takayuki Mizuno

Akira Hirano

Eiji Yoshida

Koichi Ishihara

Riichi Kudo

Etsushi Yamazaki

Yasushi Takatori

Masato Mizoguchi

Masahito Tomizawa

Munehiro Matsui

Yoshiaki Kisaka

Hiroto Kawakami

Hidehiko Takara

Takuya Oda

Takafumi Tanaka

Tetsuro Inui

Wataru Imajuku

Masanori Nakamura

Hideyuki Nosaka

Hiroshi Yamazaki

Munehiko Nagatani

Takuya Ohara

Fukutaro Hamaoka

Tetsuo Takahashi

Akihide Sano

Koki Shibahara

Tadao Nakagawa

Kazushige Yonenaga

Hirotaka Ono

Shoukei Kobayashi

Akira Isoda

Shogo Yamanaka

Shigeki Aisawa

Kohki Shibahara

Kazuhito Takei

Shoichiro Kuwahara

Mitsunori Fukutoku

Akihiko Matsuura

Kenji Sato

Shimpei Shimizu

Hiroji Masuda

Shingo Kawai

Yasuyuki Endoh

Masaki Asobe

Eiichi Yamada

Mikio Yoneyama

Hiromu Toba

Katsuyoshi Miura

Arnold Mattheus

Koichi Murata

Hiroshi Takahashi

Kenya Suzuki

Yasuyuki Inoue

Yosuke Takeuchi

Takushi Kazama

Kengo Horikoshi

Takeshi Umeki

Keita Yamaguchi

Takashi Ono

Masafumi Koga

Akio Tokura

Hirokazu Takenouchi

Werner Weiershausen

Ralph Leppla

Shigeru Ono

Kouji Enbutsu

Kazunori Senoo

Yasuyuki Endo

Tadanobu Nikaido

Fumiaki Saitou

Shoichirou Kuwahara

Isao Tomita

An interference component generated because a plurality of carrier generation units and a plurality of local oscillation units are asynchronous is used as state information, a predetermined state equation for calculating posterior state information on the basis of prior state information, and a transmission data sequence are used as observation information, a Kalman filter algorithm is applied to a predetermined observation equation for calculating the observation information in a state indicated by the posterior state information on the basis of the posterior state information calculated by the state equation, a reception data sequence, and a weight matrix to calculate a posterior state estimate of the interference component, and an estimated sequence of the transmission data sequence from which the interference component has been removed is calculated on the basis of the calculated posterior state estimate.

Signal detector, carrier phase retrieval apparatus, carrier phase retrieval method and carrier phase retrieval program

The signal detection device includes the signal detection unit that derives the estimation vector of the transmission signal vector, the first conversion unit that converts the estimation vector of the transmission signal vector to the estimation vector of the transmission signal vector based on the reduced basis, the first determination unit that converts the estimation vector of the transmission signal vector based on the reduced basis to the determination value vector of the transmission signal vector, the first update unit that updates the separation matrix, the second conversion unit that converts the first error signal vector to the second error signal vector based on the reduced basis, the second update unit that updates the error covariance matrix based on the reduced basis, the second determination unit that determines whether or not the predetermined condition is satisfied, and a third update unit that updates the unimodular matrix, the inverse matrix of the unimodular matrix, and the error covariance matrix based on the reduced basis when it is determined that the predetermined condition is established.

Signal detection apparatus, signal detection method and program

An optical transmitter includes an I-component optical modulation unit, a Q-component optical modulation unit, and a 2×2 optical coupler. The I-component optical modulation unit generates modulated light based on an I-component data signal. The Q-component optical modulation unit generates modulated light based on a Q-component data signal. The 2×2 optical coupler receives the modulated light generated by the I-component optical modulation unit from a first input port, receives the modulated light generated by the Q-component optical modulation unit from a second input port, generates two optical QAM signals having a phase conjugate relationship from the modulated light which has been input from the first input port and the modulated light which has been input from the second input port, outputs one of said two optical QAM signals from a first output port, and outputs the other one of said two optical QAM signals from a second output port.

Optical transmitter

An amplification fiber includes a core which is doped with an erbium ion and a cladding which surrounds the core and has a refractive index lower than a refractive index of the core, and a relative refractive index difference Δnbetween the core and the cladding is not more than a smaller one of values of a relative refractive index difference Δnexpressed as a predetermined expression related to a radius a of the core and a relative refractive index difference Δnexpressed as a predetermined expression related to the radius a of the core.

Amplifying fiber and optical amplifier

An optical amplifier repeater system includes an optical fiber propagating a light beam in a plurality of propagation modes and an optical amplifier repeater amplifying the light beam propagated through the optical fiber. The optical amplifier repeater includes an optical demultiplexer demultiplexing the light beam in the plurality of propagation modes propagated through the optical fiber into a plurality of single-mode light beams, an optical amplifier amplifying, by simultaneous pumping, intensities of the plurality of single-mode light beams using a light beam generated by one pumping light source, an optical multiplexer multiplexing the plurality of single-mode light beams amplified by the optical amplifier into a light beam in the plurality of propagation modes, and an optical intensity adjusting unit adjusting the intensity of each of the plurality of single-mode light beams at least one of before or after the amplification by the optical amplifier. The optical intensity adjusting unit performs the adjustment by amplifying or attenuating the optical intensity of each of the plurality of single-mode light beams in an individual optical path through which the single-mode light beam is propagated.

Light amplifying relay system

A wavelength dispersion compensating apparatus, including: a signal light generating unit which generates, from predetermined signal light, signal light having a phase correlation centered on a degenerate frequency of a phase sensitive amplifier; a dispersion compensation transmission path which compensates for a wavelength dispersion of the predetermined signal light included in the signal light; a filter which compensates for a residual wavelength dispersion after compensation by the dispersion compensation transmission path of the predetermined signal light included in the signal light; a phase sensitive amplifier which amplifies the signal light input via the dispersion compensation transmission path and the filter; a residual wavelength dispersion calculating unit which calculates a residual wavelength dispersion amount based on a measurement result of output light amplified by the phase sensitive amplifier; and a filter control unit which controls the filter so as to add a wavelength dispersion that cancels out the calculated residual wavelength dispersion amount to the predetermined signal light.

Wavelength dispersion compensation apparatus and wavelength dispersion compensation method

There is provided a multimode optical amplifier that provides gain to a plurality of propagation modes of signal light. The multimode optical amplifier includes a multiplexer that multiplexes the signal light and excitation light; an amplifying fiber which has a core that propagates a predetermined plurality of propagation modes of the signal light and a predetermined plurality of propagation modes of the excitation light, and which provides an individual gain value for each of the predetermined propagation modes of the signal light; a wavelength-flattening filter that maintains a constant gain value for a frequency for all predetermined propagation modes of the signal light; and a mode-flattening filter that maintains the gain value at a constant value for a predetermined propagation mode of the signal light for all predetermined propagation modes of the signal light.

Multimode optical amplifier

An optical transmission system including: N transmitters, each of the N transmitters being configured to convert one of N electrical signals indicating data sequences different from one another into an optical signal; a signal generator configured to cause N optical splitters to split the N optical signals output from the N transmitters to convert the N optical signals into M optical signals; a multiplexer configured to convert the M optical signals converted by the signal generator into one mode-multiplexed signal that is excitable in at least M modes; a demultiplexer configured to convert the mode-multiplexed signal converted by the multiplexer into M optical signals; M receivers, each of the M receivers being configured to convert one of the M optical signals converted by the demultiplexer into the electrical signal; and a signal detector configured to perform signal separation on the M electrical signals converted by the M receivers to extract the N data sequences.

Optical transmission system and optical transmission method

An optical transmission system includes a plurality of transmission lines through which a mode-multiplexed signal obtained by multiplexing a plurality of optical signals of different types of modes is transmitted, and one or more mode group permutation units provided between the plurality of transmission lines. The mode group permutation unit changes, on a mode-group-by-mode-group basis, an optical signal of a mode belonging to a mode group to an optical signal of another mode belonging to a mode group after permutation corresponding to the mode group in such a manner that modes are interchanged between at least some of the plurality of optical signals multiplexed into the mode-multiplexed signal input from one of the plurality of transmission lines on an input side, and outputs the mode-multiplexed signal after mode interchange to one of the plurality of transmission lines on an output side.

Optical transmission system, optical transmission apparatus and optical transmission method

An optical signal processing apparatus of an embodiment is an optical signal processing apparatus for separating and detecting an optical signal transmitted in a mode division multiplexing optical communication method by signal processing based on a multi-input multi-output (MIMO)-type linear filter. The device includes a signal processing unit configured to estimate weighting factors of the MIMO-type linear filter by sequential calculation based on an affine projection method. In the sequential calculation of the signal processing device, an output signal by the sequential calculation is expressed by a correlation vector indicating a correlation between the plurality of input signals, a smoothing prefilter vector indicating, of smoothing prefilter factors indicating a relationship between the weighting factors at current time and input signals from a first time being a past predetermined time to the current time, smoothing prefilter factors corresponding to each time from the first time to a second time that corresponds to an affine projection order in the affine projection method, and input signals from the first time to the second time.

Optical signal processing apparatus, optical signal processing method and computer program

A computation unit uses an assumed chromatic dispersion amount to compensate for dispersion of a coherently received optical signal and performs arithmetic of a signal power of the optical signal that is dispersion compensated. The computation unit performs computation of an evaluation function when a signal power and a delayed signal power obtained by applying a predetermined delay to the signal power satisfy a threshold condition. The evaluation function is a function for evaluating whether the assumed chromatic dispersion amount is a chromatic dispersion amount of the optical signal using the difference between the signal power and the delayed signal power. The chromatic dispersion amount calculation unit calculates a chromatic dispersion amount of the optical signal based on the computation result of the evaluation function by the computation unit when each of a plurality of different assumed chromatic dispersion amounts is used.

Wavelength dispersion amount calculation apparatus and wavelength dispersion amount calculation method

An optical transmission system includes: a transmission unit configured to co-propagate a signal light in which data is modulated and an idler light having complex amplitude that is phase conjugate with the signal light via an optical transmission medium; at least one optical amplifier configured to perform a phase sensitive amplification operation through an action among the signal light, the idler light, and an excitation light in a nonlinear medium; and a reception unit configured to receive the signal light that has been amplified by the optical amplifier, coherently detect the signal light and the idler light individually, and conduct a diversity synthesis to demodulate the data.

Optical transmitting system and optical transmitting method

A receiver convolutes each of a real component and an imaginary component of each polarization of a polarization-multiplexed reception signal with an impulse response for compensating for frequency characteristics of the receiver and a complex impulse response for wavelength dispersion compensation, and generates, as input signals, the convoluted real component and imaginary component of each polarization and phase conjugations thereof, for each polarization. The receiver generates, for each polarization, a first addition signal obtained by multiplying each of the real component and the imaginary component of each polarization by a complex impulse response, thereafter adding together the multiplied real component and imaginary component, and applying a phase rotation for frequency offset compensation to the added components, and a second addition signal obtained by multiplying each of the phase conjugation of the real component of and the phase conjugation of the imaginary component of each polarization by a complex impulse response, thereafter adding together the multiplied phase conjugations, and applying a phase rotation opposite to the phase rotation for frequency offset compensation to the added phase conjugations, and adds or subtracts a transmission data bias correction signal to or from a signal obtained by adding together the generated first addition signal and second addition signal.

Signal processing method, signal processing apparatus and communication system

A signal receiving apparatus includes at least one signal separating apparatus that separates a specific signal from a plurality of received signals. Each of the at least one signal separating apparatus includes a spatial filtering unit that separates at least one equalized signal and a decision signal outputting unit that generates a first decision signal by deciding the equalized signal and outputs the generated first decision signal. The spatial filtering unit separates the at least one equalized signal by multiplying at least the plurality of received signals among the plurality of received signals and either the first decision signal output from the decision signal outputting unit or a second decision signal output from another signal separating apparatus by predetermined weighting coefficients.

Signal separating apparatus and signal separating method

An optically amplified repeater system includes optical transmission paths, a multi-channel optical amplifier, one or more Raman amplification pumping light sources, and a wavelength multiplexer. The multi-channel optical amplifier includes K simultaneous pumping light sources, N optical amplification media, and one or more optical couplers, and simultaneously amplifies, with the K simultaneous pumping light sources, light intensities of optical signals that pass through the N optical amplification media and propagate through the optical transmission paths. Light intensities of the wavelength band of the optical signals is Raman amplified by the Raman amplification pumping light. A light intensity of the Raman amplification pumping light output from the one or more Raman amplification pumping light sources is determined in accordance with characteristic differences between the optical signals passing through the optical transmission paths.

Optically amplified repeater system and optical amplifier

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Yokosuka, Japan

Yutaka Miyamoto