Fujitsu Corporation

Terumi Chikama

Susumu Kinoshita

Yasushi Sugaya

Hiroshi Onaka

Takao Naito

Miki Takeda

Shigeki Watanabe

Takafumi Terahara

Hideyuki Miyata

Tetsuya Kiyonaga

Yutaka Kai

Yoshihito Onoda

Kazue Otsuka

Hideo Kuwahara

Chihiro Ohshima

Kazue Okazaki

George Ishikawa

Tadao Nakazawa

Hiroshi Nakamoto

Masuo Suyama

Naomasa Shimojoh

Hiroki Ooi

Yuichi Akiyama

Miki Onaka

Norifumi Shukunami

Etsuko Hayashi

Hiroaki Tomofuji

Tadashi Okiyama

Hiroyuki Itou

Taiki Kobayashi

Sinya Inagaki

Chiaki Ohsawa

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

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.

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.

A light branching/inserting apparatus which can easily control light signal wavelengths, and which can branch, insert or transmit light signals having an optional wavelength and optional multiplexed number, by using a wavelength selection filter utilizing acousto-optic effects. The apparatus comprises; an ADM node sectionwhich has an AOTFwith four ports as a wavelength selection filter and is connected to a transmission path, an RF signal generatorwhich generates an RF signal of an optional frequency and applies the signal to the AOTF, a selected wavelength-variable light branching sectionwhich receives and processes the light signal output from the branching port of the AOTFfor each wavelength, a light inserting sectionwhich generates an optional number of insertion light signals with optional wavelengths and sends the insertion light signals to an insertion port of the AOTF, and a monitoring sectionwhich monitors the spectrum of the light signal input/output to/from the ADM node section

Light branching/inserting apparatus and light branching apparatus using wavelength selection filter

The present invention aims to provide a WDM optical communication system that can arrange efficiently optical signals of a plurality of bit rates at different wavelength spacing. To this end, for example, a basic constitution of a demultiplexing section to be applied to the WDM optical communication system of the present invention is provided with a demultiplexer that demultiplexes WDM signal light into 2components in accordance with a plurality of wavelength regions set according to minimum wavelength spacing, 2optical switches, each of which has one input port to which light from the demultiplexer is input, and a plurality of output ports, that selects one of the plurality of output ports to connect it to the input port, and m multiplexers that each multiplexes each output light of the 2optical switches, wherein switching operations of the optical switches is set such that the bandwidth of each optical signal is approximately the same as the wavelength arrangement spacing corresponding to each bit rate.

Wavelength division multiplexing optical communication system

A rare earth element doped fiber forming an optical amplifier is pumped with a plurality of pumping lights to prevent drop of the inversion population ratio in the length direction of the rare earth element doped fiber.

Optical amplifier and method for amplifying wavelength multiplexed transmission signal light

An optical amplifier for use in, for example, a wavelength multiplexing optical communication system, in order to allow an excitation light source to be enlargeable or removable in accordance with an increase/decrease in the number of channels in signal light even if the optical communication system is in operation.

Optical amplifier, excitation light source control method for use in optical amplifier, and optical amplifier control method

A gain equalizer which equalizes gain versus wavelength characteristics of an optical amplifier. The gain versus wavelength characteristics of the optical amplifier include first, second and third gain peaks in a wavelength band with the second gain peak being between the first and third gain peaks. The optical amplifier amplifies an input signal in accordance with the gain versus wavelength characteristics to produce an output signal. The gain equalizer includes first, second and third optical filters having first, second and third transparency characteristics, respectively. The first, second and third transparency characteristics are periodic waveforms having different periods related to the wavelength difference between the first and third gain peaks. The second transparency characteristic is a periodic waveform having a period equal to 1/(2 ) of the period of the waveform of the first transparency characteristic. The third transparency characteristic is a periodic waveform having a period equal to &frac14; of the period of the waveform of the first transparency characteristic. For example, the first transparency characteristic is a periodic waveform with &frac14; period extending between the first and third gain peaks, the second transparency characteristic is a periodic waveform with one period extending between the first and third gain peaks, and the third transparency characteristic is a periodic waveform with two periods extending between the first and third gain peaks.

Gain equalizer which includes a plurality of optical filters for equalizing the gain of an optical amplifier

An optical sending apparatus of this invention includes a plurality of optical signal generating sections, a dispersion compensating section and a wavelength multiplexing section. The dispersion compensating section performs compensation with a predetermined chromatic dispersion value to at least one of polarized light generated by the optical signal generating sections while a predetermined state of polarized light is maintained. The wavelength multiplexing section combines output light outputted from the optical signal generating section with output light passing through the dispersion compensating section so that the polarized light of adjacent wavelengths crosses orthogonal to each other. The optical sending apparatus having such a construction can generate high-density WDM optical signals, the dispersion of which is compensated in advance, by a polarization crossing method.

Optical sending apparatus and channel extension method

An optical transmitter having a function which compensates for wavelength dispersion is provided with a plurality of light sources for outputting light having wavelengths that differ from one another. Before the optical transmission system begins operating, the wavelength of light output to an optical transmission line is varied by changing over the light sources in order to detect a wavelength whose transmission characteristic is optimum with regard to wavelength dispersion exhibited by this optical transmission line. During system operation, the light having the detected optimum wavelength is output to the optical transmission line.

Optical transmitter and optical transmission system

The invention provides a remote control device of an acousto-optic tunable filter, which comprises an acousto-optic tunable filter interpolated in an optical transmission line, capable of controlling an output state of an input light signal by being supplied with a surface acoustic wave control signal through a control port; a surface acoustic wave control signal source to generate the surface acoustic wave control signal, which is provided at a remote place from the acousto-optic tunable filter; and a control unit that receives an information of the surface acoustic wave control signal from the surface acoustic wave control signal source through remote transmission means, and supplies the surface acoustic wave control signal to the control port of the acousto-optic tunable filter. According to this invention, the scale of the device using the acousto-optic tunable filter becomes enlarged, the power consumption is increased; and the man power required for the maintenance of the devices can be reduced, and the remote control of the acousto-optic tunable filter can be achieved.

REMOTE CONTROL DEVICE OF ACOUSTO-OPTIC TUNABLE FILTER AND OPTICAL TRANSMISSION SYSTEM CONTAINING EQUALIZER USING ACOUSTO-OPTIC TUNABLE FILTER AND OPTICAL TRANSMISSION SYSTEM CONTAINING OPTICAL ADD/DROP MULTIPLEXER USING ACOUSTO-OPTIC TUNABLE FILTER

In an optical amplifier for use in, for example, a wavelength multiplexing optical communication system, in order to allow an excitation light source to be enlargeable or removable in accordance with an increase/decrease in the number of channels in signal light even if the optical communication system is in operation, there are included an optical amplifying section ( ) for amplifying and outputting inputted signal light, a plurality of excitation light sources ( ) and an excitation light source control section ( ) for controlling operations of the excitation light sources ( ), wherein the excitation light sources are composed of a main excitation light source ( ) and an auxiliary excitation light source ( ), and the excitation light source control section ( ) is equipped with a control section ( ) which, when the number of channels in the inputted signal light is equal to or less than a predetermined number of channels, executes control whereby the main excitation light source ( ) supplies excitation light and which executes control whereby the main excitation light source ( ) and the auxiliary excitation light source ( ) cooperatively supply excitation light when the number of channels in the signal light is more than the predetermined number of channels.

In an OADM system, an OADM device includes an AOTF. The AOTF can select an optional wavelength by changing the frequency of an RF signal to be applied. An optical signal having a specified wavelength can be dropped from a wavelength-multiplexed optical signal input from an input terminal, or a wavelength-multiplexed optical signal input from an add port can be multiplexed with a through optical signal. However, considering the increase in coherent cross talk, the AOTF should be exclusively used for dropping in an actual device configuration. Otherwise, a drop optical signal is branched by an optical coupler with the wavelength selected by a tributary station. Thus, the wavelength selected by the tributary station can be extracted by the AOTF from the through optical signal.

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Kawasaki, Japan

Terumi Chikama