Nippon Telegraph and Telephone Corporation

Ntt Electronics Corporation

Kengo Horikoshi

Yoshiaki Kisaka

Seiji Okamoto

Etsushi Yamazaki

Masanori Nakamura

Mitsuteru Yoshida

Masahito Tomizawa

Takayuki Kobayashi

Naoki Fujiwara

Koichi Ishihara

Masahiro Suzuki

Hiroyuki Uzawa

Takashi Yamada

Shuto Yamamoto

Hiroyuki Ishii

Hiroshi Yamazaki

Tomoki Murakami

Yutaka Miyamoto

Hiroshi Koizumi

Masato Mizoguchi

Hideyuki Nosaka

Yoshiaki Yamada

Riichi Kudo

Koichi Murata

Akira Masuda

Munehiko Nagatani

Yuki Yoshida

Fukutaro Hamaoka

Tomoyoshi Kataoka

Asuka Matsushita

Tomohiro Takamuku

Yasuharu Onuma

Hisao Yoshinaga

Hiroyuki Fukuyama

Eiji Yoshida

Takuya Ohara

Takashi Saida

Shin Kamei

Naoki Miura

Hiroto Kawakami

Hideki Nishizawa

Hideaki Matsuzaki

Kazushige Yonenaga

Nobuhiro Kikuchi

Hiroaki Katsurai

Kazuhito Takei

Toshihiro Itoh

Tadao Nakagawa

Shoichiro Kuwahara

Shunsuke Kanai

Takashi Mitsui

Shigeki Aisawa

Koki Shibahara

Osamu Ishida

Takahiko Shindo

Kimikazu Sano

Toshiaki Shitaba

Masafumi Nogawa

Kohki Shibahara

Mikio Yoneyama

Akihiro Tanabe

Sadayuki Yasuda

Takeo Sasai

Manabu Kubota

Eiichi Hosoya

Yves Bouvier

An aspect of the present invention is an adaptive equalization filter for an optical transmission system, including: a main signal filter; and a coefficient computation unit that updates the filter coefficient of the main signal filter. The pre-stage filter and the post-stage filter receive a sample of the main signal as an input. The pre-stage coefficient computation unit obtains the filter coefficient of the pre-stage filter by feedback control using the gradient method. The post-stage coefficient computation unit obtains the filter coefficient of the post-stage filter by feedforward control. The convolution computation unit obtains the filter coefficient of the main signal filter by convolution computation of the filter coefficient of the pre-stage filter obtained by the pre-stage coefficient computation unit and the filter coefficient of the post-stage filter obtained by the post-stage coefficient computation unit.

Adaptive equalization filter and method for updating filter coefficients

A signal processing apparatus includes: a coefficient update unit configured to approximate a characteristic of a transmission line of an optical signal by a first tap coefficient vector of which an L0 norm is a predetermined value or less; a zeroing unit configured to generate a second tap coefficient vector by replacing, with 0, a tap coefficient of which an absolute value is less than a threshold among tap coefficients of the first tap coefficient vector; and an adaptive filter configured to perform, based on the second tap coefficient vector, adaptive equalization processing on a digital signal corresponding to an optical signal received via the transmission line.

Signal processing apparatus, signal processing method, and program

An optical transmission system according to an embodiment includes: an optical transmission unit which modulates an optical signal into which a known signal is inserted and transmits the optical signal; and an optical reception unit which receives the optical signal from the optical transmission unit, wherein the optical reception unit includes: an optical receiver which performs coherent detection of a reception signal of the optical signal received from the optical transmission unit; a receiver transfer function estimation section which estimates a nonlinear response transfer function of the optical receiver based on the known signal included in the reception signal after the detection by the optical receiver; and a receiver compensation section which compensates nonlinear distortion of the reception signal after the detection based on the nonlinear response transfer function which the receiver transfer function estimation section estimates.

Optical transmission system and compensation 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 includes: a first optical transmitting unit for transmitting a first optical signal having a first wavelength; a second optical transmitting unit for transmitting a second optical signal having a second wavelength; an output adjustment unit for acquiring the first optical signal and the second optical signal, adjusting signal intensities of the acquired optical signals, and outputting the optical signals; a multiplexer for multiplexing the first optical signal and the second optical signal that have been subjected to signal intensity adjustment and outputting a multiplexed signal; an amplifier for amplifying the multiplexed signal; a first optical receiving unit for receiving the amplified first optical signal; and a second optical receiving unit for receiving the amplified second optical signal. The output adjustment unit adjusts the signal intensities of the first optical signal and the second optical signal such that the signal intensity of the first optical signal received by the first optical receiving unit is larger than or equal to a first predetermined value, and the signal intensity of the second optical signal received by the second optical receiving unit is larger than or equal to a second predetermined value.

Optical transmission system and output adjustment apparatus

A wavelength dispersion amount estimation apparatus includes a correlation signal generation unit configured to generate, from a receive signal, a first signal including a main signal of the receive signal and a second signal, which includes an image signal corresponding to the main signal, with a shift by a baud rate of the receive signal relative to the first signal in a frequency domain, a correlation calculation unit configured to calculate a cross correlation of the first signal and the second signal, and a dispersion amount calculation unit configured to calculate a wavelength dispersion amount, based on a position of a peak of the cross correlation.

Wavelength dispersion amount estimation apparatus

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.

Optical transmission system, optical receiving apparatus and optical transmission method

A method for manufacturing a monolithically integrated semiconductor optical integrated element comprising a DFB laser, an EA modulator, and a SOA disposed in a light emitting direction, comprising the step of forming a semiconductor wafer on which the elements are two-dimensionally arrayed and aligned the optical axes; cleaving the semiconductor wafer along a plane orthogonal to the light emitting direction to form a semiconductor bar including a plurality of the elements arranged one-dimensionally along a direction orthogonal to the light emitting direction such that the elements adjacent to each other share an identical cleavage end face as a light emission surface; inspecting the semiconductor bar by driving the SOA and the DFB laser through a connection wiring part together; and separating out the semiconductor bar after the inspection to cut the connection wiring part connecting the electrode of the SOA and the DFB laser to isolate from each other.

Semiconductor integrated optics element and production method therefor

A reception apparatus includes a dispersion compensation unit configured to acquire an electrical signal resulting from conversion of an optical signal and perform, on the electrical signal, dispersion compensation with a predetermined compensation amount, a clip rate measurement unit configured to measure a clip rate for the electrical signal subjected to the dispersion compensation, and a control unit configured to detect the compensation amount that minimizes the clip rate.

Receiving apparatus and receiving method

A fiber module (B) according to the present disclosure includes an input-side optical fiber (), an output-side optical fiber (), a ferrule () in which the input-side optical fiber and the output-side optical fiber are insertable in both ends and a groove () is formed in a direction orthogonal to a longitudinal direction (D) in the middle of the longitudinal direction, a dielectric multilayer film filter () inserted in the groove, and an input-side GI fiber () and an output-side GI fiber () joined by fusion to respective terminal portions of the input-side optical fiber and the output-side optical fiber. The dielectric multilayer film filter is interposed between an end surface () of the input-side GI fiber and an end surface () of the output-side GI fiber in the longitudinal direction.

Fiber module

A signal-to-noise ratio (SNR) estimation method includes an optical signal transmission step of inserting at least one pair of signal sequences into transmission data and transmitting the transmission data into which the at least one pair of signal sequences is inserted, a signal sequence extraction step of extracting the at least one pair of signal sequences from a received signal obtained by receiving the transmitted transmission data, an inner product calculation step of calculating an inner product value of the extracted at least one pair of signal sequences, a reception power calculation step of calculating reception power of the extracted at least one pair of signal sequences, and an SNR calculation step of calculating an SNR of the at least one pair of signal sequences on the basis of the calculated inner product value and the calculated reception power.

Signal-to-noise ratio estimation method, optical transmission apparatus, and optical transmission system

An optical receiver that demodulates an optical modulation signal into a baseband signal, which is an electrical signal, and decodes a received symbol acquired by converting the baseband signal. The optical receiver includes: an analog-to-digital converter that converts the baseband signal into a digital signal of which the number of samples per received symbol is M/N (samples/symbol), M and N being positive integers, M/N being not an integer, and 'M&#x3e;N' being satisfied; and an adaptive equalization processing unit that executes an equalization operation set in advance to output the received symbol on the basis of the digital signal of which the number of samples per received symbol is M/N (samples/symbol) and a predetermined tap coefficient digital signal equalization tap coefficients used for equalization of a signal, the coefficient being updated in any sampling period.

Optical receiver, optical reception method, and optical communication system

An optical transmitter of an optical data transmission system transmitting data through an optical fiber transmission path includes a main signal generator that converts first transmission data into a predetermined signal format to generate a first signal, a DCSK modulator that DCSK-modulates second transmission data to generate a second signal, a signal-multiplexer that performs time-division multiplexing of the first signal and the second signal, and an electro-optical converter that converts a multiplexed signal obtained by the time-division multiplexing of the signal-multiplexer from an electric signal into an optical signal, and outputs the optical signal to the optical fiber transmission path.

Optical transmitter, optical receiver, optical data transmission system, optical transmission method, and optical reception method

A Fourier-transformer performs Fourier transform on a filter coefficient output from an adaptive equalizer which comprises a finite impulse response filter of N taps (N represents an integer of 2 or more) in a time direction. An eigenvalue sum calculator integrates a frequency-differentiation result of the Fourier-transformed filter coefficient and a complex conjugate of the Fourier-transformed filter coefficient to calculate a matrix, and calculates a sum of two eigenvalues of the matrix. A proportionality factor calculator calculates a proportionality factor for frequency from the sum of the two eigenvalues.

Chromatic dispersion estimating circuit, optical reception device and chromatic dispersion amount estimating method

A coherent optical reception device includes a local oscillation laser that supplies laser light, a coherent optical reception front-end unit that receives a multi-level modulated optical signal, demodulates the optical signal on the basis of the laser light, and converts a demodulated optical signal into an electrical analog signal, an analog-to-digital converter that converts the analog signal into a digital signal, a compensation unit that compensates for an influence of dispersion due to a wavelength or a polarized wave of the optical signal and recovers a carrier phase of the digital signal, a constellation distortion compensation unit that compensates for constellation distortion of the multi-level modulation included in the digital signal in which an influence of dispersion is compensated for by the compensation unit, and an error correction decoding unit that performs error correction of the digital signal in which the constellation distortion is compensated for.

Coherent optical reception device

Growing community of inventors

Yokosuka, Japan

Kengo Horikoshi