Fujitsu Corporation

Tooru Matsumoto

Shoji Yoshida

Kazuo Yamane

Shota Mori

Takashi Tsuda

Makoto Takakuwa

Makoto Murakami

Hiroyuki Iwaki

Akio Morimoto

Yoshihiro Shimizu

Kazuto Imai

Tooru Shima

A transmission system includes a plurality of nodes in which respective adjacent nodes are coupled by a first kind of optical fiber compatible with light in a first wavelength band or a second kind of optical fiber compatible with light in a second wavelength band, wherein each of the plurality of nodes includes a transmitting node that generates a wavelength-multiplexed optical signal in the first wavelength band by carrying out wavelength multiplexing of a plurality of optical signals and transmits the wavelength-multiplexed optical signal, a receiving node that demultiplexes the plurality of optical signals from the wavelength-multiplexed optical signal and receives the plurality of optical signals, and one or more relay nodes that relay the wavelength-multiplexed optical signal from the transmitting node to the receiving node through the first kind or the second kind of optical fiber.

Transmission system and transmission method

An optical amplifying device disposed on a transmission path of a WDM signal includes an optical amplifier amplifying the WDM signal, a detecting unit detecting a change in a transmission wavelength count contained in the WDM signal and/or a change in light receiving level of the optical amplifier, a measuring unit measuring an optical signal to noise (SN) ratio of the WDM signal outputted from the optical amplifier, an update unit updating a reference value for evaluating the measurement value of the optical SN ratio obtained by the measuring unit when the detecting unit detects the change, a judging unit judging whether or not the measurement value deviates from an allowable range based on a reference value, and an output unit outputting an error of the optical amplifier if the measurement value deviates from the allowable range.

Optical amplifying device

An optical transmission system includes an optical wavelength branching unit that shifts a wavelength transmission band in the short-wavelength or long-wavelength directions based on a branching filter operation temperature, and performs a branching operation on a wavelength-multiplexed signal. A reception transponder performs decoding on an error correction code. An error correction monitoring unit gathers an error correction amount upon which a branching filter temperature control unit sets the branching filter operation temperature. A transmission transponder performs encoding on an error correction code. An optical wavelength combining unit shifts the wavelength transmission band in the opposite direction from the shifting direction based on a combining filter operation temperature, to perform a combining operation on optical signals and output a wavelength-multiplexed optical signal. A combining filter temperature control unit sets the combining filter operation temperature based on the error correction amount sent from the optical reception device.

Optical transmission system

The invention relates to a method of activating an optical communication system comprising a plurality of optical amplifiers having an optical amplifier, between optical transmission lines in which wavelength-division multiplex optical signals are transmitted. The method comprises steps of: generating a desired slope in a desired wavelength range of a gain wavelength curve of the optical amplifier; adjusting an output of the optical amplifier to a desired output level; performing the above two steps in a plurality of optical repeater stations, the steps being carried out in sequence from the first to the last optical repeater stations; and adjusting a level in each optical signal in the wavelength-division multiplex optical signal so as to have substantially constant optical signal-to-noise ratios in the optical signals to be received. Activating the optical communication system according to this procedure allows proper execution of gain slope compensation, output control, and pre-emphasis control.

Method of activating optical communication system, channel increasing/decreasing method, and computer-readable recording medium

The present invention discloses a fault indicator circuit in a system having a plurality of circuit blocks each provided with an individual power source. Each of the circuit blocks needs to indicate a fault when a fault occurs in the individual power source of the circuit block. The fault indicator circuit of the present invention includes a fault indicator which performs fault indication in response to a fault indication control signal from the circuit block having the fault or one of the other circuit blocks. When a fault occurs in the individual power source of a circuit block, the fault indicator performs fault indication by means of power supplied from the individual power source of one of the other circuit blocks. An input determiner which reduces the level of the fault indicator control signal outputted from one of the other circuit blocks is disposed at the input terminal of a gate circuit into which the fault indication control signal is inputted from one of the other circuit blocks. Thus, the fault indicator of each circuit block can be prevented from being wrongly activated due to a fault in the individual power source of one of the other circuit blocks.

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Kawasaki, Japan

Tooru Matsumoto