Yokogawa Electric Corporation

Fujitsu Corporation

Hitachi Cable, Inc.

Akira Miura

Tsuyoshi Yakihara

Hiroki Ooi

Chie Sato

Shinji Kobayashi

Shinji Iio

Sadaharu Oka

Morio Wada

Katsuya Ikezawa

Masayuki Suehiro

Takafumi Terahara

Takeshi Hoshida

Jens Rasmussen

Yoshiyuki Asano

Yuichi Akiyama

Daisuke Hayashi

Kentaro Nakamura

Akira Toyama

Hiroyuki Matsuura

Akihiko Isomura

Hirotoshi Kodaka

Yasukazu Akasaka

Shin-ichi Nakajima

Shinichi Nakajima

Tadashige Fujita

Hiroshi Onaka

Hiroshi Sugawara

Mamoru Hihara

Machio Dobashi

Akira Nagashima

Yasuyuki Suzuki

George Ishikawa

Hiroshi Shimizu

Toru Katagiri

Kenji Uchida

Toshiaki Kobayashi

Isao Uchida

Kousuke Doi

Yusuke Kishine

Shoujirou Araki

Tsuyoshi Yamamoto

Hisao Nakashima

Takao Naito

Yasushi Sugaya

Toshiki Tanaka

Yutaka Kai

Tomoo Takahara

Yoshinobu Kubota

Naoki Kuwata

Naoki Hashimoto

Ichiro Nakajima

Masahiro Yuki

Yasuhiro Yamauchi

Makoto Komiyama

Ryosuke Goto

Takahiro Kudo

Hiroshi Nakamoto

Takashi Mogi

Hitoshi Hara

Kiyotoshi Noheji

Hideaki Arai

Satoru Uchida

Yoshinori Nishizawa

Yoshihiro Sanpei

Toshimasa Umezawa

Minoru Akutsu

Tetsuya Ohtani

Toshimichi Suzuki

Hironori Okita

Satoshi Takasugi

Kanji Tatsumi

Ikurou Aoki

Masamichi Ohashi

Kentaro Tezuka

Shun-ichi Miyazaki

Katsutoshi Sakakibara

Yoshihito Sanpei

Tsuyoshi Takihara

Hiromi Kamata

Naoaki Machida

Shigeo Uneme

Jens C Rasmussen

A phase shift unit provides a prescribed phase difference (&#x3c0;/2, for example) between a pair of optical signals transmitted via a pair of arms constituting a data modulation unit. A low-frequency signal fis superimposed on one of the optical signals. A signal of which phase is shifted by &#x3c0;/2 from the low-frequency signal fis superimposed on the other optical signal. A pair of the optical signals is coupled, and a part of which is converted into an electrical signal by a photodiode. 2fcomponent contained in the electrical signal is extracted. Bias voltage provided to the phase shift unit is controlled by feedback control so that the 2fcomponent becomes the minimum.

Optical transmitting apparatus, optical receiving apparatus, and optical communication system comprising them

An optical transmitter is provided for transmitting a wavelength multiplexed signal comprising an intensity modulation optical signal and a phase modulation optical signal through a transmission line. The optical transmitter includes a bit time difference given signal generator for generating at least two optical signals having a bit time difference therebetween, from the wavelength multiplexed signal. The optical transmitter further includes a wavelength multiplexed signal output unit to which at least two optical signals are input from the bit time difference given signal generator, and which generates and outputs a wavelength multiplexed signal in which the bit time difference was given between the phase modulation optical signal and the phase modulation optical signal.

Optical transmitter, optical transmission method, and wavelength-selective variable delayer

An OADM in a wavelength division multiplexing transmission system includes a wavelength selection switch that selects a predetermined wavelength from a multiple optical signal obtained by multiplexing a phase modulated signal and an intensity modulated signal and outputs the selected wavelength signal to a predetermined output port. The wavelength selection switch has a different delay for each wavelength of the multiple optical signal. For example, the wavelength selection switch includes a mirror array. Optical paths from the surfaces of mirrors arranged on the mirror array to the diffraction grating are different in the case of adjacent mirrors.

Optical signal processing apparatus

In a dispersion compensating apparatus, a reference identifying unit identifies a reference (X dB down) that makes a penalty lower than a predetermined value in accordance with optical signal information and a reference identifying table, and a VIPA plate temperature adjusting unit adjusts a refractive index of a VIPA plate by modifying a temperature of the VIPA plate so that a transmission center wavelength derived from the reference matches the wavelength defined by an ITU-T Grid. If a dispersion compensation value setting unit performs an optimal residual dispersion value search, the VIPA plate temperature adjusting unit determines if a filtering penalty is lower than a predetermined value in accordance with a penalty management table. If the filtering penalty is lower than the predetermined value, temperature adjustment of the VIPA plate is not performed.

Dispersion compensating apparatus and dispersion compensating method

Where add optical signals have k different bit rates, an add controller is connected to k (&#x3c;N) of N input ports and sends the add optical signals to the k input ports to perform add control. A drop controller is connected to m (&#x3c;M) of M output ports and performs drop control on optical signals from the m output ports. The k input ports of an N&#xd7;M wavelength selective switch and the add controller are connected by k links (Lto Lk) which have introduced therein dispersion compensators for compensating chromatic dispersions of the add optical signals with the respective bit rates. The add controller selects a link through which an add optical signal is to be passed for dispersion compensation, and sends the signal to the N&#xd7;M wavelength selective switch via the selected link.

Optical transmission apparatus

An optical add/drop multiplexer includes a first optical coupler receiving an optical signal including a plurality of multiplexed wavelengths, a wavelength blocker receiving the optical signal from the first optical coupler, and blocking at least one wavelength of the plurality of multiplexed wavelengths, a first wavelength selective switch, having one input port receiving the outputted optical signal from the first optical coupler and a plurality of output ports, demultiplexing a plurality of arbitrarily selected multiplexed wavelengths from the received optical signal, a second wavelength selective switch, having a plurality of input ports, each input port receiving a different optical signal and one output port, multiplexing a plurality of arbitrarily selected wavelength signals on the plurality of input ports, and a second optical coupler receiving the optical signal output from the wavelength blocker and multiplexed wavelength signal from the second wavelength selective switch.

Optical add/drop multiplexer

A wavelength division multiplexing system according to the present art adjusts the amount of dispersion compensation (the amount of dispersion compensation of an NZ-DSF and a DCF) every all spans on the basis of the time slot when an intensity modulation signal transmitter outputs an intensity modulation signal and the wavelength interval when a wavelength coupler multiplexes a phase modulation signal (output from a phase modulation signal transmitter) and the intensity modulation signal.

Transmission system and transmission method

A dispersion compensation method comprising the steps of: a) providing a compensation node for each predetermined number of in-line repeaters; b) carrying out dispersion compensation for the in-line repeaters with the different bit rates in common; c) carrying out wavelength demultiplexing on the optical signal for each of the different bit rates in the compensation node; and d) setting an optimum dispersion compensation amount for the optical signal of each bit rate.

Dispersion compensation method and compensation node

An interferometer for demodulating a differential M-phase shift keying signal includes a PLC type interferometer main body, a heating portion that heats the PLC type interferometer main body, and an intermediate member having a higher stiffness than that of the PLC type interferometer main body, for bonding the PLC type interferometer main body and the heating portion with each other while being sandwiched therebetween. A linear expansion coefficient difference between the PLC type interferometer main body and the intermediate member is equal to or smaller than 4.5&#xd7;10/&#xb0; C., and a thermal conductivity difference between the PLC type interferometer main body and the intermediate member is equal to or larger than 10 W/mK. A phase of an optical signal flowing through the interferometer is adjusted by using the heating portion and a second heating portion.

Interferometer for demodulating differential M-phase shift keying signal

A delay interferometer and a demodulator including the delay interferometer and a balanced photodetector are provided. A half mirror splits an optical signal into first and second split beams of light which travel on first and second optical paths, respectively. A first reflector being disposed on the first optical path reflects the first split beam of light toward the half mirror. The second reflector being disposed on the second optical path reflects the second split beam of light toward the half mirror. At least one phase compensator being disposed between the half mirror and at least one of the first and second reflectors includes a medium that exhibits thermooptic effect and has temperature dependency of refractive index. The half mirror couples the first and second split beams of light to generate at least first and second coupled beams of light.

Delay interferometer and demodulator

A data modulator unit generates a DQPSK optical signal in accordance with a data signal. A phase shift unit provides a phase difference of &#x3c0;/2 between a pair of arms. A photodetector converts an output signal of the data modulator unit into an electrical signal. A filter is a low-pass filter with a cut-off frequency lower than a symbol frequency, and filters an output signal of the photodetector. A monitor unit detects power of an output signal of the filter. A phase difference control unit adjusts the amount of phase shift in the phase shift unit so as to minimize power of an output signal of the filter.

Optical transmitting apparatus and optical communication system

A core unit arranged in a transmission path includes a through path for causing an input signal to an input port to pass through to an output port, a drop-side portthat drops the input signal having a predetermined wavelength, and an add-side portthat adds channel having a predetermined wavelength to the input light.

An optical packet network system of a ring type, capable of preventing degradation of an optical signal, can be implemented by providing a mechanism relatively simple in structure, capable of erasing light noise if the optical packet signal does not exists. In the optical packet network system made up by interconnecting respective nodes adjacent to each other, and connecting a sending source of an optical packet signal to a ring, a light noise removal function block is provided between the respective nodes adjacent to each other.

Optical packet network system

A chromatic dispersion monitoring apparatus according to the present invention comprises: a photodetector which photo-electrically converts an optical signal; a low-pass filter which limits a frequency bandwidth of the photo-electrically converted electrical signal to be within a range set according to a modulation format of the optical signal and a bit rate thereof; a DC elimination circuit which eliminates a direct current component of the bandwidth limited electrical signal; and a power detector which detects the power of the bandwidth limited electrical signal to detect the residual dispersion of the optical signal. As a result, it becomes possible to easily realize the chromatic dispersion monitoring apparatus of low cost, which is also capable to be arranged on an in-line.

Chromatic dispersion monitoring method and chromatic dispersion monitoring apparatus, and optical transmission system

Growing community of inventors

Kawasaki, Japan

Akira Miura