Fujitsu Corporation

Other

Fujitsu Telecom Networks Limited

Yasushi Sugaya

Susumu Kinoshita

Etsuko Hayashi

Miki Onaka

Terumi Chikama

Tomoto Tanaka

Miki Takeda

Shinichirou Muro

Masato Nishihara

Takehiro Fujita

Hiroshi Onaka

Norifumi Shukunami

Satoru Okano

Hiroaki Tomofuji

Manabu Watanabe

Ichiro Nakajima

Hiroki Ooi

Kentaro Nakamura

Ryosuke Goto

Hideaki Sugiya

Keiko Sasaki

Kiyotoshi Noheji

Masanori Kondoh

Chihiro Ohshima

Togo Fukushi

Takahumi Terahara

Takeshi Hoshida

Akira Miura

Shinya Inagaki

Tomoaki Takeyama

Tadashi Okiyama

Takashi Hayasaka

Akira Yamamoto

Hiroyuki Itou

Yoshihito Onoda

Yoshito Kachita

Hisashi Takamatsu

Kaoru Moriya

Tomoyuki Sakata

Yuichiro Sakane

Taiki Kobayashi

Takashi Satou

Toshiki Honda

Kouichi Maeda

Rikiya Watanabe

Tsutomu Tsurumi

Hiromu Yoshii

Ryuta Hoshi

Sinya Inagaki

Manabu Watanbe

An optical transmission system includes: a first optical transmission device configured to transmit measurement light to an optical transmission line on a first direction; and a second optical transmission device configured, when an optical transmission characteristic is measured, to loop-back the measurement light received from the first optical transmission device through an optical transmission line on the first direction and to transmit the measurement light to the first optical transmission device through an optical transmission line on a second direction, wherein, when the optical transmission characteristic is measured, the first optical transmission device receives the measurement light loop-backed by the second optical transmission device and measures the optical transmission characteristic between the first optical transmission device and the second optical transmission device.

Optical transmission system and optical transmission device

An optical transmission device includes: an optical signal generator to generate and transmit an optical signal that transmits data; a detector to detect a number of active clients; and a processor to determine transmission rate of the optical signal according to the number of active clients and quality of the optical signal at an optical receiver.

Optical transmission device and optical transmission system

An optical amplifier which amplifies a wavelength division multiplexed optical signal having a variable number of channels associated with different wavelengths and outputs the amplified WDM optical signal. The optical amplifier includes a first optical amplifier which amplifies the wavelength division multiplexed optical signal and outputs the first optical amplifier amplified wavelength division multiplexed optical signal; a variable optical attenuator which controls a level of the first optical amplifier amplified wavelength division multiplexed optical signal and outputs the controlled wavelength division multiplexed optical signal; a second optical amplifier which amplifies the controlled wavelength division multiplexed optical signal and outputs the amplified, controlled wavelength division multiplexed optical signal; and a controller which controls the wavelength division multiplexed optical signal to be amplified with a constant gain.

Controller which controls a variable optical attenuator to control the power level of a wavelength-multiplexed optical signal when the number of channels are varied

An optical receiving device includes: an optical amplifier configured to amplify a wavelength multiplexed optical signal; a demultiplexer configured to demultiplex the amplified wavelength multiplexed signal into optical signals of a plurality of wavelengths; optical receivers configured to regenerate the demultiplexed optical signals; error correction units configured to correct a bit error in the regenerated optical signals; and main control unit. The control unit adjusts RXDTV of the optical receiver for receiving optical signals of a given wavelength to the optimal value in the state where the gain of the optical amplifier is lowered from that of a normal operation such that the occurrence of bit errors in the optical signals of the other wavelengths does not exceed the correction capability of the error correction unit.

Optical receiving device

A multi-wavelength light amplifier includes a first-stage light amplifier which has a first light amplifying optical fiber amplifying a light input, a second stage light amplifier which has a second light amplifying optical fiber amplifying a first light output from the first-stage light amplifier, and an optical system which maintains a second light output of the second-stage light amplifier at a constant power level. The first-stage and second-stage light amplifiers have different gain vs wavelength characteristics so that the multi-wavelength light amplifier has no wavelength-dependence of a gain thereof.

Multi-wavelength light amplifier

An optical transmission system includes an optical transmitter that sends signal light to a transmission path, an optical receiver that receives the signal light from the transmission path, and an optical amplifier that is provided on the transmission path and that amplifies the signal light, the optical amplifier being configured to control a gain characteristic of the optical amplifier such that a power of signal light having a wavelength included within a wavelength range in which polarization hole burning occurs is higher than a power of another signal light having a wavelength outside the wavelength range.

Optical transmission system

A WDM optical transmission system includes a plurality of optical nodes optically coupled by a transmission line, a processor that is operative to calculate an amount of adjustment of a reception level capable of increasing an optical signal-to-noise ratio for each channel of the WDM light reaching the optical node positioned at a receiving end of the unit section based on information on amplification operation of the WDM light in at least one optical-amplification repeating node disposed on the optical transmission line in the unit section, and to adjust a power level corresponding to each channel of the WDM light transmitted on the transmission line from the optical node positioned at a transmission end of the unit section in accordance with a calculation result of the calculation.

WDM optical transmission system and control method thereof

An optical amplifying apparatus which includes an optical amplifier, an optical attenuator and a controller. The optical amplifier amplifies a light signal having a variable number of channels. The optical attenuator passes the amplified light signal and has a variable light transmissivity. Prior to varying the number of channels in the light signal, the controller varies the light transmissivity of the optical attenuator so that a power level of the amplified light signal is maintained at an approximately constant level that depends on the number of channels in the light signal prior to the varying the number of channels. While the number of channels in the light signal is being varied, the controller maintains the light transmissivity of the optical attenuator to be constant. Subsequent to varying the number of channels in the light signal, the controller varies the light transmissivity of the optical attenuator so that a power level of the amplified light signal is maintained at an approximately constant level that depends on the number of channels in the light signal subsequent to the varying the number of channels.

To obtain automatic gain control with high accuracy by including first and second light monitors, a reference light supplying unit supplying reference light of which wavelength is set within a gain band of a distributed Raman amplification and out of a wavelength band of main signal light to the optical transmission path, a first reference light monitor monitoring a power of the reference light input to the optical transmission path from one end side thereof, a second reference light monitor monitoring the power of the reference light output from the other end side of the optical transmission path, and a controlling unit controlling supply of pump light in a pump light supplying unit as well as supervising a state of the optical transmission path, based on monitor results from the first and second light monitor and the monitor results in the first and second reference light monitors.

Distributed Raman amplifying system, start-up method thereof, and optical device

An aspect of the embodiments utilizes an optical transmission apparatus which includes a rough adjustment execution portion that monitors a bit error rate of an optical signal for set values of a dispersion compensator where the set values have been set less closely to each other within a dispersion compensation control range than when a wavelength dispersion value set in the dispersion compensator is determined, and carries out a rough adjustment to determine a comparison threshold value used to set the wavelength dispersion value based on the monitored bit error rate, and a fine adjustment execution portion that monitors the bit error rate for the dispersion compensator the set values have been set more closely to each other, and carries out an adjustment to determine a wavelength dispersion value corresponding to the midpoint between the two acquired bit error rates as the wavelength dispersion value of the dispersion compensator.

Optical transmission apparatus, optical transmission method, and optical transceiver

A WDM signal monitoring system includes a measuring unit that measures power levels in a plurality of predetermined wavelength bands about a wavelength division multiplex signal, a waveform determination unit that determines an approximate waveform of each channel from each bit rate and modulation system of a plurality of channels which forms a wavelength division multiplex signal, and an approximation unit that determines a power level and a wavelength of each channel by approximating the power level in a plurality of wavelength bands which the measuring unit measured with the approximate waveform of each channel which the waveform determination unit determined.

Wavelength division multiplex signal monitoring system and wavelength division multiplex transmission device equipped with the same

It is an object of the present invention to provide an optical amplifier using optical amplification mediums each doped with a rare earth element for increasing amplification efficiency of signal light in S-band and the like. To this end, the optical amplifier is constituted such that, when performing optical amplification for S-band and the like in which a center wavelength of a gain peak in the optical amplification medium is located at an outside of a signal band, a gain coefficient of when a pumping condition of the optical amplification medium is maximum is set so that a parameter &#x3b7; obtained by dividing a minimum value of the gain coefficient in the signal band by a maximum value of the gain coefficient outside of the signal band becomes a previously set value or more, wherein, for example, the parameter &#x3b7; can be increased by controlling a temperature of each of a plurality of EDFs between which gain equalizers are disposed.

Optical amplifier

In an optical transmission system according to one aspect of the present invention, for transmitting a WDM light from a transmission station to a reception station, utilizing a Raman amplifier, the Raman amplifier comprises: an optical amplification medium; a pumping light source generating a plurality of pumping lights having wavelengths different from each other; an optical device introducing the plurality of pumping lights to the optical amplification medium; and control means for controlling the pumping light source, the transmission station sends out a plurality of reference lights having wavelengths at which respective Raman gain obtained by the plurality of pumping lights reach peaks or wavelengths close to the above wavelengths, and the control means controls the plurality of pumping lights based on the optical powers of the plurality of reference lights. Thus, it becomes possible to accurately manage the optical power balance of the WDM light and the optical power of the entire WDM light.

Optical amplifier provided with control function of pumping light, and optical transmission system using the same

A Raman amplifier inputs pump light into an optical fiber (transmission path) through which an optical signal passes, to amplify the optical signal. An optical receiving unit is provided downstream of the Raman amplifier and monitors the power of the optical signal amplified by the Raman amplifier. A calculating unit determines Raman amplification gain based on the power of the optical signal monitored by the optical receiving unit, and calculates the power of a noise component included in the optical signal based on the gain. The calculating unit, in real-time, calculates the power, which varies in complicated manners depending on conditions, and outputs information concerning to the power to another apparatus at a frequency on the order of milliseconds.

Optical amplification apparatus, optical communication apparatus, and optical communication method

Growing community of inventors

Kawasaki, Japan

Yasushi Sugaya