Fujitsu Corporation

Hideaki Sugiya

Yoshihito Onoda

Akira Yamamoto

Haruki Tanaka

Toshihiro Suzuki

Yasushi Sugaya

Etsuko Hayashi

Hisayuki Ojima

Makoto Ohtou

Yuki Murakami

Miki Onaka

Hiroaki Tomofuji

Ichiro Nakajima

Takuji Maeda

Snigdho Chandra Bardalai

Shinichirou Muro

Yuji Tamura

Abinder S Dhillon

Shingo Hara

Sanjay Gera

Masanori Kondoh

Tatsuo Nagayoshi

Katsumi Sugawa

Vibha Chhatwal Sarin

Taichi Ueki

Takeshi Noma

Mamoru Suematsu

Yoshikazu Nakanishi

Yuya Ishida

Tomoko Murakami

Tougo Fukushi

Koji Batou

A transmission apparatus includes a mapping unit configured to map a first information associated with detecting an error of a frame into a payload area of the frame; and a transmission unit configured to transmit the frame including the first information and a second information associated with detecting an error of the frame.

Transmission apparatus and transmission method

A transmission device transmits a frame to a correspondent device and receives a frame from the correspondent device. The transmission device includes: a measurement unit configured to perform a delay measurement that measures a period of time from when a frame is transmitted to the correspondent device until when a corresponding frame is received from the correspondent device; and a delay decision unit configured to determine a transmission delay between the transmission device and the correspondent device based on a plurality of target measurement results obtained from a plurality of delay measurements except for at least a first delay measurement among delay measurements performed by the measurement unit.

Transmission device and method for measuring delay

Two rare earth-doped optical fibers are connected in series and used to amplify input light. A splitter is installed between these two rare earth-doped optical fibers. The input light is monitored by having the portion of the input light that is branched off, by the splitter received by a photodiode. Excitation light output from a laser light source is guided by optical couplers and supplied to the above rare earth-doped optical fibers. A control circuit controls the output light level and, at the same time, stops the output from the laser light source when the input light level drops below a specified threshold value. The gain of the first stage rare earth-doped optical fiber while excitation light is being supplied is larger than the loss that occurs due to branching of the input light by the splitter.

Optical amplifier and an optical amplification method

Even during a protection period in which a state transition is not caused from an ALC state to an ALD state, when an output light level that is inputted is below a threshold for ALC transition read from a memory, a processor causes a transition by switching an internal state from an ALC state to an ALD state. Then, an ALD operation is started, outputting a control voltage to a VAT control unit so as to achieve a predetermined fixed attenuation amount.

Optical transmitting apparatus and optical multiplexing unit

An optical wavelength multiplexing system includes transmission-side and reception-side optical wavelength multiplexers, and terminal devices, which are connected to each other by optical fiber cables. Optical wavelength converters in the transmission-side optical wavelength multiplexers are connected to ports respectively. The optical wavelength converter converts an input optical signal into an arbitrary preset wavelength to generate a converted optical signal. The port has a predetermined wavelength preset therein. Each optical power level of input converted optical signals is compared with each optical power level of optical signals of respective wavelengths set in the ports. When a difference is detected in the comparison result, it is determined that an optical wavelength converter is incorrectly connected to the port.

Optical wavelength multiplexing system, optical wavelength multiplexing method, and computer product

In particular embodiments, providing signal reachability information to a network includes establishing signal reachability information at a network node of the network. The signal reachability information describes attributes that affect reachability of an optical signal. The signal reachability information is inserted into an advertisement, and the advertisement is sent to network nodes of the network.

Providing signal reachability information to a network

The present invention relates to an apparatus for controlling a gain of an optical amplifier, and the apparatus comprises a target gain calculating unit for calculating, as a target gain for an optical amplifier, a value obtained by increasing or decreasing a gain (output) of signal light as the number of wavelengths of wavelength-multiplexed signal light decreases, and a control signal outputting unit for outputting a control signal to the optical amplifier so as to amplify the wavelength-multiplexed signal light with the target gain calculated by the target gain calculating unit. This promptly suppresses a fluctuation of signal light level, particularly, a fluctuation of output light power of an optical amplifier stemming from a variation of the number of wavelengths of wavelength-multiplexed signal light.

Gain control apparatus, optical transmission apparatus, gain control method for optical amplifier, and wavelength multiplex optical transmission system

The present invention relates to an optical transmission apparatus capable of suppressing a transitional gain variation when a number of signal wavelengths changes, and maintaining communication quality in optical signals. The optical transmission apparatus is provided with an optical power control device that varies light power of light for each wavelength component corresponding to a wavelength channel, the light including signal light and spontaneous emission light; a wavelength arrangement information obtaining unit that obtains arrangement information of the wavelength channel of the signal light; and a control unit that controls the power control device based on the arrangement information obtained at the wavelength arrangement information obtaining unit so that light power of a wavelength component of the signal light and light power of a wavelength component other than the wavelength component of the signal light become substantially equal.

Optical transmission apparatus and method of controlling the same

A transmission apparatus designed to be capable of monitoring faults which occur between the input stage of an optical multiplexer and the input stage of an optical amplifier, appropriately switching between automatic gain control and automatic level control, and outputting signal lights with appropriate optical power, without using a spectrum analyzer. The optical multiplexer combines the wavelengths of a plurality of signal lights. The optical amplifier is connected at the latter stage of the optical multiplexer, and operates in the automatic gain control mode or in the automatic level control mode, the automatic gain control mode maintaining a constant gain for wavelength-multiplexed signal light, the automatic level control mode maintaining constant output power for the wavelength-multiplexed signal light. A mode selector selects the automatic gain control mode or the automatic level control mode for the optical amplifier based on the total optical power of the plurality of signal lights to be input to the optical multiplexer and the optical power of the wavelength-multiplexed signal light to be input to the optical amplifier.

Optical transmission apparatus with automatic gain control and automatic level control mode selection

An optical amplifier may be quickly returned from a shutdown state to a regular state after getting recovery information of a fault. Gain setting by ASE is conducted to the repeaters on the up-stream side during the shutdown state, by outputting ASE light with the same intensity as the WDM signal. Accordingly, before realizing the recovery of shutdown, the gain setting is completed with the light whose intensity is within the safe criterion. After realizing the recovery of shutdown, the optical transmission system can be returned quickly to the regular operating state after recovery of shutdown state.

Optical transmission system

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

An optical transmission system is provided which is capable of booting the system by using an ASE (Amplified Spontaneous Emission) light in a manner to provide high quality. A pre-amplifier receives noise light and does gain setting in an amplifier booting mode and receives an optical signal and to amplify the received signal in a working mode. A variable dispersion compensator is placed in a preceding-stage of the pre-amplifier and makes compensation of dispersion of a wavelength occurring when an optical signal propagates through an optical fiber in a variable manner. A switching unit to select, when the noise light passes through the variable dispersion compensator, if a level of the noise light is deviated from a desired level, a bypass route so as to make the noise light not be input to the variable dispersion compensator but be input to the pre-amplifier in an amplifier booting mode according to a switching instruction and to select a passage route so as to make the optical signal, after having been input to the variable dispersion compensator and having undergone dispersion compensation, be input to the pre-amplifier according to the switching instruction in a working mode.

An optical amplifier, provided in a WDM transmission system, contains an amplification medium for amplifying WDM light, a measurement part for measuring at least one input optical power of the WDM light on both input and output sides of the amplification medium, a variable gain equalizer for variably setting a passing-wavelength characteristic, a database for holding data representing wavelength characteristics that respectively correspond to transmission line types, an arithmetic part for computing an inverted passing-wavelength characteristic resulting from a passing-wavelength, based on an acquired transmission line type, the optical power measured by the measurement part, and the data held in the database, and a setting part for setting a passing-wavelength characteristic of the variable gain equalizer, based on the inverted passing-wavelength characteristic computed by the arithmetic part, and with this, capable of controlling optical filters more quickly and amplifying optical signals more efficiently in WDM systems.

Optical amplifier with variable gain equalization

Two rare earth-doped optical fibers are connected in series and used to amplify input light. A splitter is installed between these two rare earth-doped optical fibers. The input light is monitored by having the portion of the input light that is branched off by the splitter received by a photodiode. Excitation light output from a laser light source is guided by optical couplers and supplied to the above rare earth-doped optical fibers. A control circuit controls the output light level and, at the same time, stops the output from the laser light source when the input light level drops below a specified threshold value. The gain of the first stage rare earth-doped optical fiber while excitation light is being supplied is larger than the loss that occurs due to branching of the input light by the splitter.

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Kawasaki, Japan

Hideaki Sugiya