Nippon Telegraph and Telephone Corporation

Shuto Yamamoto

Yoshiaki Kisaka

Masanori Nakamura

Seiji Okamoto

Akira Masuda

Hiroki Taniguchi

Tetsuro Inui

Hideki Nishizawa

Seiki Kuwabara

Kenya Suzuki

Osamu Moriwaki

Keita Yamaguchi

Shunichi Soma

Fukutaro Hamaoka

Mitsunori Fukutoku

Asuka Matsushita

Kengo Horikoshi

Masahito Tomizawa

Takayuki Kobayashi

Takafumi Tanaka

According to an aspect of the present invention, there is provided an optical signal demodulator including an optical reception unit, an AD conversion unit, a digital signal processing unit, and a signal determination unit, in which the signal determination unit includes: a spectrum shaping filter processing unit that receives a reception signal sequence of the digital signal from the digital signal processing unit and outputs a value obtained by performing a convolution operation on the reception signal sequence which is received; a transmission line simulation filter processing unit that outputs a value obtained by performing a convolution operation on a candidate signal sequence which is determined based on a symbol transition of the reception signal; an error information acquisition unit that acquires error information between the value output from the spectrum shaping filter processing unit and the value output from the transmission line simulation filter processing unit; and a bit determination unit that determines a value of a bit included in the symbol transmitted by a transmission unit based on the error information acquired by the error information acquisition unit.

Optical signal demodulator, control method and program

The symbol determination device generates the plurality of estimated reception symbol sequences on the basis of the estimated transfer function of the transmission line represented by the tap gain value applied to each tap of the nonlinear filter including the plurality of taps and the plurality of candidate symbol sequences, determines the transmission symbol by the maximum likelihood sequence estimation on the basis of the determination target reception symbol sequence obtained from the reception signal sequence and each of the plurality of estimated reception symbol sequences, identifies the estimated transmission symbol corresponding to the determination target reception symbol sequence, calculates the new tap gain values on the basis of the determination target reception symbol sequence and the identified estimated transmission symbol sequence, updates the estimated transfer function by applying the calculated tap gain values to the taps of the transmission line estimation unit, and selects the tap to be used on the basis of the magnitude of the calculated new tap gain value and the predetermined tap gain threshold value.

Symbol determination device and tap selection method

An optical transmission system is an optical transmission system for transmitting a signal from an optical transmitter to an optical receiver via at least a transmission line among one or more optical nodes and the transmission line, wherein the optical transmitter includes a digital filter that compensates for, between ripple components that are micro-fluctuating components in a frequency region representing a transmission characteristic of the signal in the optical transmitter and the optical receiver and non-ripple components of the transmission characteristic, at least the ripple components of the transmission characteristic, and at least one of the optical node and the optical transmitter includes an optical filter that compensates for the non-ripple components of the transmission characteristic.

Optical transmission system, control apparatus, optical transmission method and program

A high-performance optical and electronic integrated switch capable of effectively extending the transmission distance includes a network processor that controls the functions of the packet switch, a plurality of optical transceivers provided near the processor and having a photoelectric conversion function, and an optical relay switch. A plurality of optical waveguides are connected to the input and output sides of the optical relay switch. Each optical transceiver has a regeneration function that performs optical-electrical conversion on inputted optical signals, then turns back the converted signals, and performs signal conversion on them, and its input side is connected with a routing optical waveguide included in the optical waveguides on the output side of the switch and its output side is connected with a routing optical waveguide included in the optical waveguides on the input side of the switch. The optical waveguides include ones for connecting to an external communication counterpart.

Optical and electronic integrated switch

A virtual environment optical communication network is generated by setting configuration parameters of physical packages of a real environment optical communication network in package emulators that a computer program has virtually constructed to implement the physical packages, the real environment optical communication network being constructed by a plurality of node devices in which the physical packages are mounted, pieces of configuration data are generated based on pieces of resource data indicating resources required for optical paths detected based on acquired configuration parameters and a requested transmission mode, optical paths are set in the virtual environment optical communication network based on the generated pieces of configuration data, and optical paths are set in the real environment optical communication network based on the pieces of configuration data that have been used to set the optical paths.

Optical communication network management apparatus

An optical and electronic integrated switch includes a network processor that controls the functions of the packet switch, a plurality of optical transceivers having photoelectric conversion functions, and a plurality of optical switches. The optical switches include different types of optical core switch and a plurality of optical-path selection switches. The optical transceivers provided near the processor have a regenerative relay function that regenerates optical signals and turns back the optical signals, and perform optical communication with a communication counterpart via the optical switches. In the optical communication, optical switches of the different types can cooperate to set paths for optical cut-through in which path selection is performed such that inputted optical signals are outputted without the intervention of the processor. This optical cut-through can be effectively performed without imposing a signal processing burden that consumes electric power on the processor.

A photonics-electronics convergence switch with which, even if an optical network system is built by combining a plurality of packet switches, the amount of processing in the packet switches does not increase, the optical network system operates with low electric power consumption, and this enables wide-range optical communication between the nodes of a communication origin and of a communication partner, includes a network processor that is an electronic circuit configured to control the functions of the packet switch, a plurality of optical transmitter-receivers having photoelectric conversion functions, and a plurality of optical switches. Different types of optical switches cooperate to select a path through which inputted optical signals or optical signals inputted from a different packet switch connected to the packet switch are outputted to a different packet switch without passing through the processor and a path through which inputted optical signals or optical signals inputted from a different packet switch pass through the processor and are subjected to photoelectric conversion.

A photo-electron fusion switch that can perform optical communications without any trouble, even when nodes of a communication source and a communication partner that are large in transmission capacity are connected, and makes it possible to realize a concentrated arrangement of devices having similar functions and reduce the communication processing time is connected to communication source's information processing devices and communication partner's information processing devices and information processing devices that are each different in transmission speed so as to configure an optical network system. The photo-electron fusion switch includes a network processor of an electronic circuit for controlling packet switch functions, a plurality of optical transmitter/receivers that can support coherent communications and has a photoelectric conversion function capable of transmitting and receiving optical signals different in transmission speed, an optical line switching device, and a plurality of multiplexing/separators. Each multiplexing/separator simultaneously transmits and receives respective optical signals different in transmission speed to and from the nodes via optical waveguides.

Optical and electronic integrated switch and optical network system

A tentative decision is made for symbols on the basis of a received signal and a decision threshold, and a tentative decision signal including a sequence of the symbols is output. A scale value indicating a rate of increase or reduction of the received signal or a threshold change rate indicating a degree of change in the decision threshold is updated so that an appearance frequency of each of symbols included in the tentative decision signal matches an appearance frequency of each of symbols in a reference signal obtained by modulating a transmitted signal with a modulation method used in transmission which is shared between a transmitting side and a receiving side, and an SN ratio is calculated using the scale value or the threshold change rate when a degree of agreement between the appearance frequencies is within a predetermined permissible range. When the scale value is updated, a tentative decision is made for the symbols on the basis of the received signal increased or reduced by the updated scale value and the decision threshold, and when the threshold change rate is updated, the tentative decision for the symbols is made on the basis of the received signal and the decision threshold to which the updated threshold change rate is applied.

S/N ratio estimation circuit, and adaptive filter circuit

An optical transmitter generates symbols for transmission by applying a predetermined coding method to each of m-valued transmission symbols generated from transmission data, generates signal light by performing optical modulation on the basis of the symbols for transmission, and transmits the signal light. An optical receiver generates a series of digital signals from the received signal light, detects coded symbols by applying predetermined digital signal processing to the series of digital signals, decodes the m-valued transmission symbols from the detected coded symbols, and restores the transmission data from the decoded m-valued transmission symbols. An operation based on the predetermined coding method performs nonlinear coding that generates the coded symbols by generating m-valued intermediate symbols from the m-valued transmission symbols, the nonlinear coding restricting transitions between series of the coded symbols in time series by assigning bit information to a state transition between coded symbols adjacent in time series and making a number of states that each of the coded symbols can take on greater than a number of states of the m-valued transmission symbols.

Optical transmission system, optical transmitting apparatus and optical receiving apparatus

A device generates a symbol sequence by performing adaptive equalization by an estimation inverse transfer function of a transmission line on a reception signal sequence extracted from the transmission line, and performing provisional determination on the symbol sequence generated; generates a plurality of the symbol sequences indicating transmission line states in a range of a provisional determination symbol provisionally determined and nearby symbols of the provisional determination symbol; generates, based on the plurality of the symbol sequences indicating the transmission line states generated and an estimation transfer function of the transmission line, an estimation reception symbol sequence for each of the transmission line states; calculates a metric between the symbol sequence obtained from the reception signal sequence and each of a plurality of the estimation reception symbol sequences; selects a most likelihood estimation reception symbol sequence of the plurality of the estimation reception symbol sequences, based on the calculated metric, the provisional determination symbol, and the nearby symbols of the provisional determination symbol; and determines a transmission symbol sequence.

Symbol judgement apparatus and symbol judgement 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

An optical transmission system including an optical transmitter and an optical receiver, wherein the optical transmitter includes a signal coding unit that performs non-linear block coding on an M (M is an integer greater than or equal to 1)-value symbol sequence or a bit sequence input as data information to generate an L (L is an integer greater than or equal to 2, L&#x3e;M)-value symbol sequence that corresponds to the M-value symbol sequence or the bit sequence in one-to-one correspondence, a digital-to-analog conversion unit that converts the generated L-value symbol sequence to an analog signal, and a modulator that generates an optical modulation signal by performing modulation based on the analog signal, and the optical receiver includes a light receiving unit that receives the optical modulation signal transmitted from the optical transmitter and converts the optical modulation signal to an electrical signal, and a signal decoding unit that restores the M-value symbol sequence or the bit sequence by performing processing that is the reverse of processing performed by the signal coding unit, on the electrical signal.

Optical transmission system

Provided is an optical transmission system that includes an optical transmitter, and an optical receiver. The optical transmitter includes: a signal coding unit configured to perform nonlinear trellis coding, which corresponds to nonlinear calculation, on a symbol sequence; and a modulator configured to modulate the symbol sequence subjected to the nonlinear trellis coding by the signal coding unit, and transmit the modulated symbol sequence to the optical receiver. The optical receiver includes: a light receiving unit configured to receive an optical signal transmitted from the optical transmitter, and convert the received optical signal into an electrical signal; and a digital signal processing unit configured to perform digital signal processing on the electrical signal to reconstruct the symbol sequence.

There are provided an optical transmission apparatus that subjects a transmission signal including a plurality of sequences to Hadamard transform to obtain a signal in which a predetermined delay is added to one of the sequences, optically modulates the obtained signal, and transmits the modulated signal, and an optical reception apparatus that demodulates a reception signal received from the optical transmission apparatus by subjecting the reception signal to adaptive equalization processing with a predetermined number of taps. The optical reception apparatus includes: an adaptive equalization processing unit that subjects the reception signal to adaptive equalization processing of wavelength distortion compensation with a number of taps obtained by subtracting a number in accordance with the delay from the predetermined number of taps; a delay compensation unit that subjects the reception signal subjected to the wavelength distortion compensation to delay compensation in accordance with the delay; and an inverse Hadamard transform unit that subjects the reception signal subjected to the delay compensation to inverse Hadamard transform.

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Yokosuka, Japan

Shuto Yamamoto