Nippon Telegraph and Telephone Corporation

Takayuki Kobayashi

Yutaka Miyamoto

Koichi Ishihara

Etsushi Yamazaki

Riichi Kudo

Akihide Sano

Tadao Nakagawa

Yasushi Takatori

Masato Mizoguchi

Eiji Yoshida

Munehiro Matsui

Masahito Tomizawa

Tatsuya Shimada

Hiroshi Ou

Masanori Nakamura

Kengo Horikoshi

Shogo Yamanaka

Yoshiaki Kisaka

Daisuke Hisano

Shimpei Shimizu

Hideyuki Nosaka

Jun Terada

Seiji Okamoto

Mitsuteru Yoshida

Fukutaro Hamaoka

Kazushige Yonenaga

Tomoyoshi Kataoka

Eiichi Yamada

Mitsuteru Ishikawa

Naoki Fujiwara

Hiroyuki Uzawa

Munehiko Nagatani

Hidehiko Takara

Takuya Ohara

Takushi Kazama

Shuto Yamamoto

Hiroshi Yamazaki

Yukio Tsukishima

Masahiko Jinno

Kohki Shibahara

Toshihide Yoshimatsu

Kozicki Bartlomiej

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

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

An electric digital received signal obtained from a received optical signal is segmented into blocks of a certain length with an overlap of a length determined in advance with an adjacent block. Fourier transformation is performed for each of the blocks. The blocks subjected to the Fourier transformation are stored consecutively in time series, a coefficient determined based on a wavelength dispersion compensation amount according to one of frequency positions and a delay amount according to one of the frequency positions and one of time positions is applied to each of frequency component values included in a plurality of the stored blocks, and the blocks to which the coefficient has been applied and which are obtained by adding up the frequency component values to which the coefficient has been applied for each of the frequency positions are generated. Inverse Fourier transformation is performed on the generated blocks to which the coefficient has been applied. A part of the overlap subjected to the inverse Fourier transformation is removed.

Wavelength dispersion compensation apparatus, optical receiving apparatus, wavelength dispersion compensation method and computer program

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

An optical transmission system includes an optical transmitter and an optical receiver. The optical transmitter includes a low speed signal generation unit configured to generate, based on an input signal of a transmission data sequence and a signal obtained by cyclically shifting a spectrum of the input signal, a plurality of low speed signals, a high speed signal generation unit configured to digital-to-analog convert and synthesize the plurality of low speed signals to generate a high speed signal, and an optical modulation unit configured to transmit an optical signal obtained by modulation of the high speed signal to a transmission path. The optical receiver includes a reception unit configured to receive the optical signal from the transmission path and output the high speed signal obtained from the optical signal that is received, an optical-receiver-side high speed signal compensation unit configured to compensate, based on the high speed signal output by the reception unit and a signal obtained by cyclically shifting a spectrum of the high speed signal, for the high speed signal, and a reception data decoding unit configured to decode the high speed signal compensated by the optical-receiver-side high speed signal compensation unit to restore binary information included in the optical signal transmitted by the optical transmitter.

Optical transmitting system, optical transmitting apparatus, optical receiving apparatus and transfer function estimating method

An optical transmission device includes a bandwidth allocator that periodically reads bandwidth request information indicating a bandwidth required for a termination device to transmit an uplink signal from a storage and allocates a bandwidth to the termination device on the basis of the read bandwidth request information, and a timing adjuster that adjusts a period at intervals of which the bandwidth allocator reads the bandwidth request information from the storage on the basis of the timing at which resource information used to generate the bandwidth request information is received from an upper device.

Optical transmission device and bandwidth allocation method

Information on allocation of a bandwidth of uplink communication of each of user devices is extracted from information notified from an upper-level device on the uplink communication of the user devices. Correspondence information is created to indicate a correspondence among the upper-level device, the terminal device, the lower-level device, and the user device. A start time point of the uplink communication of the terminal device and an information amount of signals for which transmission of the uplink communication of the terminal device is allowed are allocated to the terminal device on the basis of the information on allocation of the bandwidth of the uplink communication of each of the user devices and the correspondence information.

Terminal station device and bandwidth allocation method

A relay transmission system includes a relay unit configured to relay uplink signals and downlink signals in the first and second communication systems, a time division duplex (TDD) information estimation unit configured to estimate a transmission period of network devices in the first communication system on the basis of the uplink or downlink signal of the first communication system that is relayed by the relay unit, a surplus bandwidth determination unit configured to determine a surplus bandwidth in which an uplink signal of the first communication system is not allocated to a relay target of the relay unit during the transmission period on the basis of the number of network devices and a maximum transmission capacity of the network devices, and a bandwidth allocation unit configured to allocate the uplink signal of the second communication system to the relay target of the relay unit in the surplus bandwidth.

Relay transmission system, relay transmission method, and relay transmission device

A terminal station device is a terminal station device of a communication system in which a high-order device, the terminal station device, an end-terminal device, and a low-order device are communicably connected in this order, the high-order device notifies the low-order device of resource information indicating a resource that is usable in communication, and thereby the resource is allocated to the low-order device. The terminal station device includes: a band allocation unit that allocates a band that is permitted to be used by the end-terminal device for transmission processing to the terminal station device, based on an interval at which the terminal station device has received the resource information.

Terminal station apparatus and band allocation method

Information on allocation of a bandwidth of uplink communication of each user device is extracted from information notified by an upper-level device on the uplink communication of the user devices. Identification information of a lower-level device connected to a terminal device and identification information of the user devices are stored in correlation with each other. A bandwidth demanded for uplink communication of the terminal device is determined on the basis of the information on the allocation of the bandwidth of the uplink communication of each of the user devices and the identification information of the user devices. A start time point of the uplink communication of the terminal device and the amount of information of signals for which transmission of the uplink communication of the terminal device is allowed are allocated to the terminal device on the basis of the bandwidth demanded for the uplink communication of the terminal device.

An increase in circuit scale is suppressed and a phase variation caused in a transmission path or the like is compensated for. An optical transmission system includes: a pilot symbol detection unit which detects a plurality of pilot symbols intermittently inserted into a received complex electric field signal that is obtained through coherent detection for a received optical signal; an error signal computation unit which calculates a complex electric field error signal indicating a phase variation at each pilot symbol based on the pilot symbols detected by the pilot symbol detection unit and a predetermined reference symbol; a compensation electric field signal generation unit which estimates a phase variation between the pilot symbols in the received complex electric field signal using filter processing based on the complex electric field error signal calculated by the error signal computation unit; and a phase noise compensation unit which performs phase compensation for the received complex electric field signal based on the phase variation between the pilot symbols estimated by the compensation electric field signal generation unit.

Optical transmission system, phase compensation method, and optical reception apparatus

The optical receiving device with phase compensation apparatus uses coherent opto-electric conversion and is designed for receiving phase- or quadrature-amplitude-modulated optical signals. The phase compensation apparatus includes following elements: a carrier-phase estimation unit that estimates carrier phase errors in a received symbol string; a gain adjustment unit that adjusts weighting of each symbols in phase error evaluation performed in the carrier-phase adjustment unit; a phase-cycle-slip reduction unit with a phase-cycle-slip detector using statistical processing performed on the output symbols from the carrier-phase estimation unit; and a phase compensation circuit that compensates carrier phase errors of the received signal using an output from the carrier phase estimation unit.

Optical receiving device and phase cycle reduction method

To enable signal position detection, frequency offset compensation, clock offset compensation, and chromatic dispersion amount estimation in a communication system based on coherent detection using an optical signal, even on a signal having a great offset in an arrival time depending on a frequency due to chromatic dispersion. An optical signal transmitting apparatus generates specific frequency band signals having power concentrated on two or more specific frequencies and transmits a signal including the specific frequency band signals. An optical signal receiving apparatus converts a received signal into a digital signal, detects positions of the specific frequency band signals from the converted digital signal, estimates frequency positions of the detected specific frequency band signals, and detects a frequency offset between an optical signal receiving apparatus and an optical signal transmitting apparatus. Moreover, the optical signal receiving apparatus detects a clock offset between the optical signal receiving apparatus and the optical signal transmitting apparatus from an interval between the estimated frequency positions of the specific frequency band signals. Furthermore, the optical signal receiving apparatus estimates temporal positions of the detected specific frequency band signals and detects a chromatic dispersion amount from a difference between the temporal positions of the specific frequency band signals corresponding to different frequencies.

Signal generating circuit, optical signal transmitting apparatus, signal receiving circuit, method for establishing optical signal synchronization, and optical signal synchronization system

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Yokosuka, Japan

Takayuki Kobayashi