Fujitsu Corporation

Hiroaki Tomofuji

Motoyoshi Sekiya

Hiroshi Nishimoto

Hiroki Ooi

George Ishikawa

Takuji Maeda

Takeshi Sakamoto

Hiroshi Onaka

Ichiro Nakajima

Yuji Shimada

Yasushi Sugaya

Toru Katagiri

Makoto Murakami

Miki Onaka

Kazuo Yamane

Satoru Okano

Takehiro Fujita

Noriaki Mizuguchi

Hideki Kobayashi

Taizo Maeda

Hiroshi Hamano

Tetsuo Wada

Tatsuo Nagayoshi

Takahumi Terahara

Takafumi Terahara

Norifumi Shukunami

Terumi Chikama

Yuichi Suzuki

Hideaki Sugiya

Tatsuya Tsuzuki

Yoshihito Onoda

Hisayuki Ojima

Chihiro Ohshima

Akihiko Sugata

Haruki Tanaka

Kenichi Kaburagi

Rikiya Watanabe

Koji Batou

Hideto Saito

An optical transceiving apparatus includes an optical transmitting device performing polarization multiplexing on and transmitting as polarization multiplexed signal light, a first signal light of a predetermined polarization direction and a second signal light of a polarization direction different from the predetermined polarization direction; an optical receiving device receiving the signal light transmitted from the optical transmitting device through an optical transmission path; an acquiring unit acquiring information indicative of magnitude relation of intensity between the first signal light and the second signal light included in the signal light received by the optical receiving device; and a control unit controlling the magnitude relation of intensity between the first signal light and the second signal light included in the signal light output from the optical transmitting device, to be opposite to the magnitude relation indicated by the information acquired by the acquiring unit.

Optical transceiving apparatus, optical transmitting method, and optical transmitting device

A transmission device includes: a wavelength detector configured to detect a first wavelength of a first optical signal; a wavelength selective switch to which the first optical signal is input; and a controller configured to detect a direction toward which a central wavelength of a passband of the wavelength selective switch is shifted from the first wavelength detected by the wavelength detector and to control the wavelength selective switch so as to increase a width of the passband toward an opposite direction of the direction toward which the central wavelength of the passband is shifted from the first wavelength.

Transmission device, transmission system, and method for adjusting passband

The present invention relates to prevention of erroneous connection in an optical network and, in particular, it provides an optical communication node having route switching function as well as an optical network system using the same in a wavelength division multiplex (WDM) network system. There is provided an optical communication node that is connected to a specific optical path in an optical network, the optical communication node having: an external network that is placed thereunder; and an interruption part for interrupting connection between the optical network and the external network, wherein the interruption part interrupts the connection until a sequence of changing a route is completed when the route setting of the optical path is changed.

Optical communication node and optical network system

An optical node apparatus according to the present invention amplifies a WDM signal light input to an input port, and thereafter, branches the amplified WDM signal light by an optical branching coupler to send the branched lights to first and second optical paths, and selects the light propagated through the first optical path by an optical switch to amplify the selected light by a post-amplifier, thereby outputting the amplified light from an output port, when the optical node apparatus is operated as an optical amplification repeating node. When the operational state is upgraded to an optical add/drop multiplexing node, an OADM section is connected between a set of connecting ports on the second optical path, and the adjustment of the OADM section is performed utilizing the WDM signal light branched by the optical branching coupler, and thereafter, the switching of the optical switch is performed to select the light on the second optical path side. As a result, since the switching the operational state from the optical amplification repeating node to the OADM node can be performed in a short time, it becomes possible to provide the continued communication service at the low initial installation cost.

Method of upgrading optical node, and an optical node apparatus

An optical transmission system with automatic startup functions to optimize the power level of optical signals entering each optical amplifier and operate those amplifiers in appropriate mode. In the process of starting up an optical transmission system, upstream and downstream optical transmission devices set up themselves under the coordination of their internal controllers. The downstream device controller adjusts its local variable optical attenuator by utilizing optical noise emission from a post-amplifier in the upstream optical transmission device, and it selects and sets a preamplifier unit to work in appropriate operating mode. The upstream device controller, on the other hand, selects and sets operating mode of its local post-amplifier unit. During this process, the upstream and downstream device controllers exchange messages over supervisory control channels to achieve the purpose.

Optical transmission system with automatic signal level adjustment and startup functions

An optical-level control apparatus includes a plurality of variable optical attenuators each used for attenuating an input optical signal included in a wavelength division multiplexing signal as a component having a specific wavelength by applying a variable attenuation quantity, a plurality of control units each used for executing automatic control for automatically controlling the attenuation quantity in order to adjust the optical level of an optical signal output by a corresponding one of the variable optical attenuators to a target level in an ordinary normal state of the input optical signal, and a detection unit for detecting a loss of light failure of an optical signal input to each of the variable optical attenuators and detecting disappearance of the loss of light failure. When the detection unit detects the loss of light failure, a corresponding one of the control units executes first attenuation quantity locking control to adjust the attenuation quantity to a first predetermined value and as the detection unit detects the disappearance of the loss of light, the corresponding control unit executes second attenuation quantity locking control to adjust the attenuation quantity to a second predetermined value.

Optical-level control method, optical-level control apparatus and wavelength-multiplexing optical network

Disclosed herein is an optical node device applicable to an optical network including a closed loop provided by an optical fiber. This optical node device includes a tunable wavelength selecting element adapted to input WDM signal light obtained by wavelength division multiplexing a plurality of optical signals having different wavelengths, the tunable wavelength selecting element having a function of dropping at least one optical signal from the WDM signal light and a function of adding at least one optical signal to at least one unassigned wavelength channel of the WDM signal light; and a wavelength selecting filter optically connected to the tunable wavelength selecting element for removing noise present in any bands other than a signal band of each optical signal passing through the tunable wavelength selecting element. With this configuration, the oscillation of optical power in the closed loop can be prevented by the use of the wavelength selecting filter for removing noise in any bands other than the signal band.

Optical node device and system including the device

In an optical signal level control apparatus used in a WDM system, the amount of circuitry per wavelength is reduced. Optical power level is detected on the output side of a variable optical attenuator, and the amount of attenuation in the variable optical attenuator is adjusted so that the output level becomes equal to a constant value L1. At this time, if the detected level is lower than a threshold value Th0 or Th-d, it is determined that a signal off condition has occurred, and the amount of attenuation is set to a constant value A1. The amount of attenuation, A1, is chosen to be sufficiently larger than the amount of attenuation used in the output level constant control but small enough to be able to detect the restoration of the signal. When the amount of attenuation is being held at the constant value A1, if the output level is restored to a level higher than the threshold value Th0 or Th1 (Th1&#x3c;Th-d), the output constant control is resumed.

Optical signal level control apparatus

A method for switching a transmission route in an optical network. A regenerator station extracts a main signal, and detects the input level of the main signal. When the input level falls below a threshold, the regenerator station determines that a failure occurs, and stops output of a main signal from the regenerator station, and transmits a control signal indicating occurrence of the failure to a receiver station, which separates the control signal from a main signal transmitted thereto, detects the input level of the main signal at the receiver station, analyzes the separated control signal, and determines whether or not a failure occurs. When the input level of the main signal at the receiver station falls below a threshold, or when the separated control signal indicates occurrence of a failure, the receiver station detects the occurrence of the failure, and switches the transmission route.

Method for switching transmission route, and optical transmission device

A multiplex optical communication system transmitting a multiplex optical signal between terminal equipments each including converters producing optical signals combined to the multiplex optical signal, through repeater equipment including an optical amplifier, under controlling the amplifier so that when a converter is added or removed, a time constant of the amplifier is equal to a time constant of the added or removed converter, or the amplifier produces output under constant output level control before adding or removing the converter and after the amplifier produces final output and constant gain control during the added or removed converter increases or decreases output. The time constant control is performed to the amplifier by making the amplifier repeat start and stop of increasing or decreasing output step by step in accordance with prescribed objective values corresponding to half way output of the optical amplifier.

Multiplex optical communication system

An optical communication apparatus performs wavelength division multiplexing with respect to signals of a plurality of signal transmission bands. The apparatus includes a first optical unit which effects distributed Raman amplification and has a characteristic that compensates for dispersion of a transmission path to which the optical communication apparatus is connected, with respect to at least one of the signal transmission bands.

Optical communication apparatus, system, and method that properly compensate for chromatic dispersion

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

Growing community of inventors

Kawasaki, Japan

Hiroaki Tomofuji