Nippon Telegraph and Telephone Corporation

Ntt Electronics Corporation

Tomoyoshi Kataoka

Masahiro Suzuki

Masahito Tomizawa

Yoshiaki Kisaka

Etsushi Yamazaki

Koichi Ishihara

Akira Hirano

Kengo Horikoshi

Kazushige Yonenaga

Mikio Yoneyama

Seiji Okamoto

Mitsuteru Yoshida

Naoki Fujiwara

Hiroyuki Uzawa

Takayuki Kobayashi

Takuya Ohara

Hiroto Kawakami

Akihide Sano

Shoichiro Kuwahara

Shigeki Aisawa

Gentaro Funatsu

Akihiko Matsuura

Hiroshi Yamazaki

Masanori Nakamura

Tomoki Murakami

Hiroshi Koizumi

Masato Mizoguchi

Hideyuki Nosaka

Yoshiaki Yamada

Riichi Kudo

Koichi Murata

Katsuya Tanaka

Norio Sato

Munehiko Nagatani

Hiroyuki Fukuyama

Takashi Saida

Yosuke Takeuchi

Shin Kamei

Kei Kitamura

Mitsuhiro Teshima

Nobuhiro Kikuchi

Etsu Hashimoto

Hiroaki Katsurai

Tadao Nakagawa

Toshihiro Itoh

Mitsunori Fukutoku

Masafumi Nogawa

Kohki Shibahara

Masahiro Tachibana

Yves Bouvier

Yuya Oyama

Akio Sahara

An optical modulator driver circuit () includes an amplifier (, Q, Q, R-R), and a current amount adjustment circuit () capable of adjusting a current amount of the amplifier () in accordance with a desired operation mode. The current amount adjustment circuit () includes at least two current sources (IS) that are individually ON/OFF-controllable in accordance with a binary control signal representing the desired operation mode.

Optical modulator driver circuit and optical transmitter

An optical signal transmission apparatus includes a modulation unit which modulates a transmission signal, a training signal sequence generation unit which generates a plurality of signal sequences having power concentrated in a plurality of different frequency bands, at least one of an amplitude and a phase of the plurality of signal sequences being modulated, as a training signal sequence, a signal multiplexing unit which appends the training signal sequence to the transmission signal, and an electro-optical conversion unit which converts a signal sequence obtained by appending the training signal sequence to the transmission signal into an optical signal and transmits the optical signal.

Optical signal transmission apparatus and optical signal transmission method

A transport apparatus includes: a client signal transceiving unit which transceives a client signal; a line signal transceiving unit which performs electric-optic conversion on a line signal to be transmitted, transmits an optical line signal, performs optic-electric conversion on a received line signal, and outputs an electrical line signal; and a plurality of signal processing units which perform signal processing on the client signal to generate the line signal to be transmitted and perform signal processing on the electrical line signal to generate the client signal. Each of the plurality of signal processing units includes a signal transceiving unit which performs transfer of a branched signal obtained by branching a signal to be transmitted and a merged signal obtained by merging received signals with another signal processing unit, and the signal transceiving unit of each of the plurality of signal processing units and the signal transceiving unit of the other signal processing unit are coupled via an inter-chip wiring.

Transport apparatus and transport method

A light modulation device detects a power of the modulated optical signal modulated by each of an I-component optical modulator and a Q-component optical modulator, synchronously-detects a component of a frequency fd from the power of the modulated optical signal, outputs a dither signal of a frequency fd/n (where n is a positive integer equal to or larger than 1) applied to a first bias voltage or a second bias voltage when adjusting the first bias voltage or the second bias voltage, outputs two dither signals having a frequency fd/m (where m is a positive integer equal to or larger than 1, where n&#x3c;m), which are mutually orthogonal to each other, applied to the first and second bias voltages when adjusting a third bias voltage, and adjusting bias voltages by increasing or decreasing bias voltages based on a synchronous detection result.

Light modulation device and light modulation method

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

The estimation of an amount of chromatic dispersion using a training signal sequence is possible. A transmission method includes: a training signal sequence generation step of generating, as training signal sequences, a plurality of signal sequences having power concentrated in a plurality of frequency bands, the power concentrated at different frequency bands; a training signal sequence selection step of selecting at least one training signal sequence from among the plurality of training signal sequences generated in the training signal sequence generation step, a signal multiplexing step of generating a signal sequence obtained by time-division multiplexing the training signal sequence selected in the training signal sequence selection step with a transmission data sequence, and an electrical-to-optical conversion step of transmitting the signal sequence generated in the signal multiplexing step as an optical signal.

Coherent communication system, communication method, and transmission method

A wavelength selection switch system includes a wavelength selection switch including an input port and an output port, a nonvolatile memory in which configuration information for controlling an operation of the wavelength selection switch is stored, a high-speed memory in which reading and writing can be performed at a higher speed than in the nonvolatile memory and that stores a copy of the configuration information stored in the nonvolatile memory, and a control unit that controls an operation of the wavelength selection switch based on the configuration information read from the high-speed memory, wherein the control unit periodically reads the configuration information stored in the nonvolatile memory and writes a copy of the read configuration information to the high-speed memory.

Wavelength selection switch system and method for controlling wavelength selection switch

An optical transmission system is provided in which the optimum operating point of a Mach-Zehnder interferometer, matched to the optical frequency of the light source on the transmitting side, can be set. The optical receiver () has an infinitesimal-modulated signal component detection circuit (), which uses the signal train output from a balanced detection circuit () to detect the infinitesimal-modulated signal component applied to the phase adjustment terminal () of an MZI () by an infinitesimal-modulated signal oscillation circuit (); a synchronous detection circuit (), which synchronously detects the infinitesimal-modulated signals output from the infinitesimal-modulated signal component detection circuit () and infinitesimal-modulated signal oscillation circuit () and detects the error signal component arising from the shift between the optical signal carrier frequency and the optical frequency characteristic of the MZI (); and a controller (), which outputs a control signal to adjust the phase difference between two split optical signals output from the MZI () so as to correct the shift amount.

Optical transmission system, optical transmitter for optical transmission system, and optical receiver for optical transmission system

The optical transmission circuit of the present invention has an optical modulatorwhich modulates continuous light at wavelength &#x3bb;o with a signal at repetition frequency fo Hz and outputs alternating phase-inverted pulse light; a bias voltage applying unitwhich applies a bias voltage to the optical modulator; an optical power spectrum measuring unithaving frequency resolution of less than fo Hz which measures the optical power spectrum of light output from the optical modulator; and a control circuit which controls the bias voltage via the bias voltage applying unitbased on measurements of the power spectrum of the output light of the optical modulator, so as to minimize the power intensity of the carrier spectrum component of wavelength &#x3bb;o, or to maximize the power intensity of the spectrum component in both side bands.

Optical transmission circuit

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Yokosuka, Japan

Tomoyoshi Kataoka