Kokusai Denshin Denwa Kabushiki Kaisha

Other

Mitsubishi Denki Kabushiki Kaisha

Kokusai Denshin Denwa Co., Ltd.

Kdd Submarine Cable Systems, Inc.

Kddi Corporation

Kdd Corporation

Kddi Submarine Cable Systems Inc.

Hidenori Taga

Shu Yamamoto

Noboru Edagawa

Shigeyuki Akiba

Masatoshi Suzuki

Noriyuki Takeda

Itsuro Morita

Koji Goto

Hiroharu Wakabayashi

Tadayoshi Kitayama

Takayuki Miyakawa

Takashi Mizuochi

Katsuhiro Shimizu

Kiwami Matsushita

Hideaki Tanaka

Takeshi Komiya

Keiji Tanaka

Hideo Yoshida

Yoshihiro Yoshida

Kazuo Kubo

Takanori Inoue

Shinichi Nakagawa

Kuniaki Motoshima

Hidenori Takahashi

Shiro Ryu

Takehiro Tsuritani

Hiroshi Ichibangase

Aritomo Uemura

Eiichi Shibano

Tadami Yasuda

Katsumi Takano

Kaoru Imai

Tetsuyuki Miyakawa

A measurement apparatus includes: a light source unit configured to generate optical signals of, from among n+1 frequencies (n is an integer of 3 or larger) at a predetermined frequency interval, n frequencies except for a target frequency, and output the generated optical signals to an optical transmission path that is a measurement target; an optical power measurement device configured to measure of an optical signal of the target frequency output from the optical transmission path and generated in the optical transmission path as a result of four-wave-mixing of the optical signals of the n frequencies; and a processor configured to determine a power spectrum density of non-linear interference noise that occurs in the optical transmission path, by multiplying the power of the optical signal of the target frequency by an adjustment value.

Measurement apparatus of optical communication system

A transmission wavelength band in an optical transmission line is divided into a plurality of sub-bands and signal lights or an ASE dummy light is disposed per sub-band as a unit. The optical power of the ASE dummy light in each sub-band is controlled so as to realize the gain profile at a full implementation in the optical transmission line. While new signal lights are being added, the optical power of whole ASE dummy lights or the optical power of the ASE dummy lights in sub-bands adjacent to the sub-band in which the new signal lights are to be added is controlled while increasing the optical power of the new signal lights so that the transmission characteristics of the existing signal lights are not affected by the signal addition.

Method for upgrading an optical transmission system and an optical transmitter

An optical receiving apparatus includes a signal brancher for branching an optical input signal received from an optical transmission line into a first signal component and a second signal component, a clock extractor for extracting a clock having an amplitude from the second signal component, and a discriminator for discriminating the first signal component. The apparatus also includes a threshold controller for generating a discrimination threshold for the discriminator according to a relationship between the extracted clock amplitude and a bit error rate to which the extracted clock amplitude corresponds.

Optical receiving apparatus and method

In an FEC frame structuring method, and an FEC multiplexer, the order of information is changed by a first interleaving circuit, a first error correction code is generated by an RS (239, 223) coding circuit, the order is returned to the original order by a first deinterleaving circuit, and a second error correction code is generated by an RS (255, 239) coding means. The second error correction code is decoded by an RS (255, 239) decoding circuitto correct errors in the information, the order of information is changed by a second interleaving circuit, the first error correction code is decoded by an RS (239, 223) decoding circuitto correct residual errors in the information, and the order is returned to the original order by a second deinterleaving circuit

FEC frame structuring method and FEC multiplexer

An optical receiving apparatus according to the present invention comprises an optical signal branching circuit for receiving a signal light input from an optical transmission line, a discriminator for discriminating an output signal of the optical signal branch circuit, an evaluator for evaluating characteristics of another output signal of the optical signal branching circuit. The evaluator includes a saturable absorber for determining the discrimination threshold of the discriminator.

An object of the present invention is to realize almost the same transmission characteristic in all wavelengths at a transmission rate of 10 Gb/s or more. An optical transmitter outputs WDM signal light multiplexed with signal light of a plurality of wavelengths toward an optical transmission line . The optical transmission line comprises an optical transmission fiber , an optical repeating amplifier and a dispersion compensating fiber . The gain characteristic of the optical repeating amplifier is set so that the gain becomes the maximum at the effective zero dispersion wavelength of the optical transmission line and that lowers inversely proportional to the distance from the effective zero dispersion wavelength. The whole optical transmission line is set so that the peak power deviation between the effective zero dispersion wavelength &lgr;0 and the wavelength &lgr;1 or &lgr;n on both end becomes approximately 4 dB.

WDM optical transmission system and an optical transmission line thereof

Method for manufacturing optical fiber cable with optical fibers whose chromatic dispersion value are uniformed

To increase the number of multiplexed wavelengths and to improve transmission characteristics in a wavelength-division-multiplexed transmission, a bandwidth compressor for bandwidth-compressing the wavelength-division-multiplexed signal light is disposed at a front part of respective optical amplifiers and a bandwidth expander for bandwidth-expanding the wavelength-division-multiplexed signal light output from said optical amplifiers is disposed at a rear part of said optical amplifiers.

Optical amplifying transmission system and optical amplifier

A laser diode continuously laser-oscillates and its output light is applied to an optical modulator. A pulse driver drives the optical modulator according to a data to be transmitted. A phase modulator is driven by a phase modulator driver and phase-modulates the output from the optical modulator. The polarization direction of the incident light of the phase modulator is set so that the modulation efficiency of the phase modulator becomes the maximum. The output light of the phase modulator inputs a birefringent medium and applies to an optical transmission line after transmitting the birefringent medium. The principal axis of the birefringent medium is disposed so as to be at an angle of 45&deg; to the polarization direction of the output light from the phase modulator.

Optical transmitting apparatus

Detection of an optical pulse position uses an optical pulse string with a determined repetitive ratio and an electric clock signal with a same frequency as the repetitive ratio of the optical pulse string. A phase of the electric clock signal oscillator is shifted and supplied to an optical modulator. The optical modulator modulates the optical pulse string based on the electric clock signal and outputs a modulated optical signal. A photo detector converts the modulated optical signal output from the optical modulator to an electric signal. The phase shift amount of the electric clock signal is controlled to maximize an output from the photo detector. Additionally, a dither signal may be used in the control of the phase shift, more than the optical modulator may be employed, and/or more than color light source may be employed. The use of at least one of feed forward and feedback control provided by maximizing an output of the photo detector allows an optical pulse having a short width to be realized.

Optical pulse position detecting circuit and an optical pulse generating apparatus and their methods

An optical wavelength division multiplexed signal amplifying repeater capable of doubling the number of wavelength division multiplexed signals that can be transmitted is disclosed. Optical signals of both 1.3 &mgr;m band and 1.55 &mgr;m band in the entered optical wavelength division multiplexed signals are amplified, while pumping lights capable of causing Raman amplification in the 1.3 &mgr;m band are coupled with the optical wavelength division multiplexed signals so as to cause the Raman amplification for the optical signals of the 1.3 &mgr;m band, such that a difference between the loss in the 1.3 &mgr;m band and the loss in the 1.55 &mgr;m band due to the optical fibers are compensated. An optical communication transmission line using such repeaters is also disclosed.

Optical wavelength division multiplexed signal amplifying repeater and optical communication transmission line with very large capacity

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 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

When an intensity modulating operation and a phase modulating operation are carried out by employing a 2-electrode MachZehnder type optical modulator preferably a LN-MZ type optical modulator, a drive signal of this 2-electrode LN-MZ type optical modulator is produced from an intensity modulation signal and a phase modulation signal with a low loss and a simple arrangement. A optical modulating apparatus includes a splitter/combiner structured to split an intensity modulation signal inputted into a first input terminal into a first electric signal having an in-phase relationship with that of the intensity modulation signal and second electric signal having an inverse phase relationship therewith, split a phase modulation signal inputted into a second input terminal into a third electric signal having an in-phase relationship with that of the phase modulation signal an also a fourth electric signal having an in-phase relationship therewith, combine the first electric signal with the fourth electric signal to thereby output a first combined signal, and combine the second electric signal with the third electric signal to thereby output a second combined signal; and an optical modulating means structured to split a light carrier wave entered from a light source into two light carrier waves, and to optically modulate the two sets of the split light carrier waves by using the first combined signal and the second combined signal derived from the splitter/combiner, and combine the two phase-modulated above said light carrier waves to output an optical modulation signal.

Optical modulating apparatus

Growing community of inventors

Tokyo, Japan

Hidenori Taga