Kokusai Denshin Denwa Kabushiki Kaisha

Other

Mitsubishi Denki Kabushiki Kaisha

Kokusai Denshin Denwa Co., Ltd.

Kdd Corporation

Kdd Submarine Cable Systems, Inc.

Kokusai Denshin Denwa K.k.

501 Kokusai Denshin Denwa Kabushiki Kaisha

Shigeyuki Akiba

Shu Yamamoto

Masatoshi Suzuki

Katsuyuki Utaka

Hidenori Taga

Noboru Edagawa

Kazuo Sakai

Yuichi Matsushima

Yukio Horiuchi

Itsuro Morita

Yukio Noda

Yukitoshi Kushiro

Noriyuki Takeda

Masashi Usami

Hideaki Tanaka

Takaya Yamamoto

Takayuki Miyakawa

Hiroharu Wakabayashi

Tadayoshi Kitayama

Kuniaki Motoshima

Kiwami Matsushita

Chuichi Ota

Aritomo Uemura

Koji Goto

Kenichi Iga

Eiichi Nakagawa

Fujio Tanaka

Yasuharu Suematsu

Junichiro Yamashita

Naoki Norimatsu

Yoshio Itaya

Yasuyuki Okamura

Haruo Abe

Katsumi Takano

Masanobu Kodaira

Shigehisa Arai

Kaoru Imai

The optical amplifier according to the present invention is constructed such that the amount of the electric current fed to the power feeding lineis first detected by the current detection means, and then a setting signal is generated to each of the bypass circuitsandin accordance with the thus detected amount of the fed current, and thereafter the output level of each of the optical repeater circuitsandis controlled respectively by the bypass circuitsand, so that the output level of these repeater circuitsandcan be controlled in accordance with the amount of the current fed to the power feeding line

Optical amplifier having various control circuitry

The optical amplifier according to the present invention is constructed such that the amount of the electric current fed to the power feeding line is first detected by the current detection means, and then a setting signal is generated to each of the bypass circuits and in accordance with the thus detected amount of the fed current, and thereafter the output level of each of the optical repeater circuits and is controlled respectively by the bypass circuits and , so that the output level of these repeater circuits and can be controlled in accordance with the amount of the current fed to the power feeding line

An optical repeater monitoring system, according to the invention, comprises an oscillating source, a reference signal transmitter for transmitting a reference signal of a predetermined frequency generated from an output of the oscillating source to a first optical fiber, and an optical repeater. The optical repeater has a first photodetector for converting light from the first optical fiber into an electrical signal, a reference signal extractor for extracting a component of the reference signal from an output of the first photodetector, a carrier generator for generating a carrier from an output of the reference signal extractor, a monitor signal modulator for modulating the carrier generated by the carrier generator with a monitor signal showing a operating state of the optical repeater, a transmitter for transmitting an output of the monitor signal modulator to a second optical fiber. The system further comprises a demodulating signal generator for generating a demodulating signal from either of the output from the oscillating source and the reference signal, the demodulating signal having a frequency equal to that of the monitor signal carrier, a second photodetector for photodetecting the light propagated on the second fiber, and a monitor signal demodulator for demodulating the monitor signal from outputs of the second photodetector and demodulating signal generator.

Optical repeater monitoring system and a method thereof

A control signal superimposer for superimposing a control signal on a signal light, comprising a pumping light source for generating a pumping light with intensity fluctuation in accordance with the control signal; a Raman amplification medium pumped by the pumping light from the pumping light source for Raman-amplifying the signal light; a combiner for combining the pumping light output from the pumping light source and the signal light to be Raman-amplified and then supplying them to the Raman amplification medium; and an optical filter for extracting the signal light component from the output light of the Raman amplification medium and terminating the pumping light component.

Control signal superimposer

An optical amplifying transmission system comprising a first optical amplifying transmission line including a first optical amplifier, a second optical amplifying transmission line including a second optical amplifier, a pumping light generator for generating pumping lights to be supplied to said first and second amplifiers, the powers of the pumping lights being variable, and first and second terminal stations which connect respectively to both ends of said first and second optical amplifying transmission lines.

Optical amplifying transmission system and optical amplifying repeater

A wavelength division multiplexed optical processing device and an optical communication transmission path which are capable of significantly improving the transmission characteristic of wavelength division multiplexed optical signals. A wavelength division multiplexed optical processing device is formed by a first arrayed optical waveguide for demultiplexing entered wavelength division multiplexed optical signals, and outputting demultiplexed optical signals; a plurality of correction units for correcting respective optical signals demultiplexed by the first arrayed optical waveguide; and a second arrayed optical waveguide for multiplexing optical signals corrected by the correction unit, and outputting multiplexed optical signals. An optical communication transmission path is formed by an optical transmission path; and at least one wavelength division multiplexed optical processing device using an arrayed optical waveguide having a transmission wavelength characteristic with a flat top shape, which is inserted into the optical transmission path at a prescribed interval.

Wavelength division multiplexed optical processing device and optical communication transmission path

An oscillator oscillates at a predetermined reference frequency, and a reference signal light sender generates light (reference signal light) of a specific wavelength deeply modulated by output from the oscillator. A frequency divider frequency-divides the output from the oscillator into a certain number, and outputs a tone signal of a predetermined measurement frequency. Output from the frequency divider is applied to selected one of a plurality of optical transmission signal senders via one of a plurality of switches, and is used to slightly intensity-modulate a corresponding optical transmission signal. An optical divider in an optical repeater outputs most of output light from an optical amplifier onto an optical fiber transmission line toward a terminal station, and applies small amounts of the light to a measuring circuit. The measuring circuit synchronously detects the measurement frequency component in the received light using the reference frequency obtained from the reference signal light of the specific wavelength. A modulator slightly varies the amplification gain of the other optical amplifier that amplifies the signal light travelling on the other optical fiber transmission line in response to results of measurement by the measuring circuit.

Optical power measuring system terminal station and repeater therefor

An equalizing apparatus for equalizing gains of wideband wavelength-division multiplexed light and for improving the S/N ratio comprises a plurality of optical amplifyer for optically amplifying light in different wavelength groups, respectively; and multiplexer for multiplexing optically amplified light from said plurality of optically amplifying means.

Gain equalizing apparatus

A new two-way WDM optical transmission system is provided. The WDM optical transmission system comprises a two-way optical fiber cable, a first dispersion compensation optical fiber (DCOF) connected to one end of the optical fiber cable, a second DCOF connected to another end of the optical fiber cable, a chromatic dispersion compensating transmitter unit and a chromatic dispersion compensating receiver unit. The two-way optical fiber cable comprises a plurality of segments. The first DCOF is connected to one end of the optical fiber cable and has a compensation amount of a half of a one segment dispersion D.sub.c of the optical fiber cable. The second DCOF is connected to another end of the optical fiber cable and has the compensation amount of the half of the one segment dispersion D.sub.c. And the chromatic dispersion compensating transmitter unit compensates accumulated residual chromatic dispersions to be caused by higher-order wavelength dispersion of the optical fiber cable at each signal wavelength. Further, the chromatic dispersion compensating receiver unit compensates accumulated residual chromatic dispersions caused by higher-order wavelength dispersion of the optical fiber cable at each signal wavelength. The chromatic dispersion compensating transmitter unit has a plurality of optical transmitters, a multiplexer combining a plurality of different wavelength bands and a plurality of chromatic dispersion compensators. And the chromatic dispersion compensating receiver unit has a demultiplexer, a plurality of optical receiver and a plurality of chromatic dispersion compensators.

Wavelength-division multiplexing optical transmission system

An optical transmission device using return-to-zero optical pulses as transmission optical pulses, which is capable of enhancing a transmission distance as well as a wavelength range with satisfactory transmission characteristics and enabling an easy realization of the wavelength division multiplexing optical transmission. The optical transmission device is formed by an optical transmitter for transmitting transmission optical pulses by superposing digital data signals onto return-to-zero optical pulses, and a modulator for applying one of a phase modulation and a frequency modulation in synchronization with a transmission rate of the transmission optical pulses, to the transmission optical pulses transmitted by the optical transmitter. This optical transmission device can be utilized in forming a wavelength division multiplexing optical transmission apparatus and an optical transmission system.

Optical transmission device, WDM optical transmission apparatus, and

This invention provides the gain equalizer positioned to an optical amplifying transmission line for equalizing gains of said optical amplifying transmission line, comprising a plurality of first optical filters varying transmittance periodically in at least predetermined wavelength range, and one or more second optical filters that their transmittance peaks at a wavelength substantially coinciding to the predetermined transmittance bottom wavelength of the first optical filters and decreases in a predetermined range at both side of the predetermined transmittance bottom wavelength.

Gain equalizer and optical amplifying transmission line

An optical transmission system comprises transmission optical fibers 14 connected between an optical transmission terminal 10 and an optical receiving terminal 12 via optical amplifying repeaters 16, and equalizing fiber 18 each connected in each equalizing interval. The equalizing fiber 18 is typically located at the terminal end of each equalizing interval. Each transmission optical fiber 14 is a dispersion-shifted fiber whose wavelength dispersion is substantially zero in a specific band, for example, 1.5 .mu.m. The optical amplifying repeaters 16 include an optical amplifier, and a dispersion compensating optical element having wavelength dispersion characteristics that exhibit an inclination opposite from that of wavelength characteristics of wavelength dispersion of the transmission optical fiber 14 (more specifically, a minus inclination with respect to the wavelength). The dispersion compensating optical element compensates offset values of cumulative wavelength dispersion among different wavelengths. The dispersion compensating optical element can be made by a fiber grating technology.

Optical transmission system and optical repeater

An optical transmission system for optical transmission with the capacity of 100 Gb/S over a distance of 9,000 km or more includes an light sending station for outputting an optical signal in the band of 1.55 .mu.m, and an light receiving station connected to the light sending station by an optical fiber transmission line. The optical fiber transmission line includes a plurality of transmission optical fibers connected by optically amplifying repeaters. Each transmission optical fiber is a single-mode optical fiber having an effective cross-sectional area of 80 .mu.m.sup.2 or more. Each optically amplifying repeater includes an erbium-doped optical fiber for pumping in 0.98 .mu.m, WDM coupler for demultiplexing and multiplexing 1.55 .mu.m and 0.98 .mu.m wavelengths, optical isolator and gain equalizing filter, which are connected in series, so as to locate output light from an pumping laser for oscillation in 0.98 .mu.m onto the erbium-doped optical fiber through the WDM coupler.

Optically amplifying/repeating transmission system and optical amplifier

The present invention is directed towards an optical ADM apparatus provided with a narrow band-pass filter which is capable of minimizing declination of the transmission characteristics. An optical transmission prohibiting element composed of an optical isolator and a fiber grating is connected in series to the downstream of a fiber grating interposed between two optical circulators. The drop light is reflected by the fiber grating and released from an output optical fiber of the optical circulator. A leak component of the drop light having passed through the fiber grating appears on the side of the isolator and runs across the isolator to the other fiber grating. Most of the leak component is however reflected by the fiber grating while its small portion enters the optical circulator via the fiber grating. The small portion of the leak component is as small as negligible and will hardly interfere with the add light. The optical transmission prohibiting element may be an optical circulator.

Optical add-drop multiplexer

An optical add/drop multiplexing scheme capable of reducing the degradation of the transmission characteristic due to the beat noises caused by the interference of the fiber grating leakage components. An optical add/drop multiplexing device is formed by a high speed polarization scrambler for entering signal lights with a data modulation at a high speed bit rate applied thereto, and scrambling polarization states of entered signal lights at high speed, and an optical add/drop element for receiving the signal lights with the polarization states scrambled by the high speed polarization scrambler, and carrying out an add/drop multiplexing operation for signal lights in a specific wavelength among received signal lights. The high speed polarization scrambler scrambles the polarization states of the entered signal lights so as to lower a probability for having worst polarization states of signal lights and interference lights, by scrambling the polarization states of the entered signal lights into every possible polarization states at nearly equal probabilities.

Growing community of inventors

Tokyo, Japan

Shigeyuki Akiba