Fujitsu Corporation

Fujitsu Telecom Networks Limited

Kazuhiro Kunimatsu

Takeshi Ono

Toshiki Honda

Hiroya Egoshi

Shota Mori

Tsukasa Takahashi

Katsumi Fukumitsu

Mitsuya Kawashita

Akio Takayasu

Tadashi Soga

Yukiko Miyazaki

Masakazu Ozaki

A transmission device includes a control card and a plurality of IF cards. The control card receives first set time from a host PC and calculates second set time by adding add time corresponding to one cycle of a clock signal that is commonly used by the control card and the IF cards to the first set time. The control card distributes the second set time to each of the IF cards. After each of the IF cards receives the second set time and sets the second set time in an internal timer, when a clock signal is detected, each of the IF cards starts a time measuring operation of the internal timer from the second set time.

Transmission device and time synchronization method

A dispersion compensation device includes a variable dispersion compensator configured to subject an input optical signal to dispersion compensation, an optical receiver configured to convert an optical signal subjected to dispersion compensation into an electrical signal, recover a clock signal and a received data signal from the electrical signal, and output clock lock information indicating whether the clock signal is locked to the electrical signal, a signal processor configured to output bit error rate information on the received data signal, and a controller configured to variably control a dispersion compensation value of the variable dispersion compensator based on the bit error rate information and the clock lock information.

Variable dispersion compensation device

A wavelength division multiplexing device comprises a detection unit to detect the low-frequency signal in the optical signal; and a control unit to control to make the dispersion compensator perform a compensation operation by determining that the optical signal is being input when a low-frequency signal is detected in the optical signal in the detection unit, and to control to stop a compensation operation of the dispersion compensator by determining that there is an input break of the optical signal when a low-frequency signal is not detected in the optical signal in the detection unit.

Wavelength division multiplexing device and method of detecting input break of optical signal

An optical signal, which is a low-speed signal superimposed on a high-speed phase modulated optical signal by intensity modulation, is used. In an optical receiver apparatus, a received signal is split, and one of the split signals is O/E converted and low frequency component alone is extracted via a filter. A clock is extracted from low-frequency component by CDR, and is compared with a preset frequency. Using the frequency difference obtained, dispersion compensation is performed with low accuracy. Next, the amount of phase control of the delay interferometeris adjusted so that the amplitude of the electrical signal is maximized. An error rate is measured, and fine adjustment is performed to improve the error rate.

High-speed dispersion compensation control apparatus

A transponder in a wavelength division multiplexing apparatus detects a wavelength of a leak light (received light) having one of plural wavelengths multiplexed or divided by a WDM unit, the leak light having been received from the WDM unit when the transponder is connected to the WDM unit; determines a transmission wavelength which is a wavelength of a light to be transmitted to the WDM unit on the basis of the wavelength of the received light; and sets to convert the wavelength of the light to be transmitted to the WDM unit into the transmission wavelength, and transmit the converted light.

Wavelength division multiplexing apparatus

A LAN signal transmission method and a transmission apparatus using the method are disclosed. A first transmission apparatus extracts only a data section of a LAN signal that is received, and accommodates the data section in a digital wrapper signal. Link information between a first LAN apparatus is accommodated in the overhead of the digital wrapper signal, and the digital wrapper signal is transmitted to a second transmission apparatus. The second transmission apparatus extracts the data section of the digital wrapper signal and the link information from the overhead of the digital wrapper signal that is received. The LAN signal that contains the data section and the link information is constituted, and transmitted to a second LAN apparatus. If the extracted link information indicates 'link down', the LAN signal to the second LAN apparatus is shut down, and the link information concerning the second LAN apparatus indicating 'link down' is masked, the link information being transmitted to the first LAN apparatus.

LAN signal transmitting method and apparatus adapted to shut down a LAN signal if extracted link information indicates link down

The present invention relates to a wavelength multiplexing apparatus for multiplexing and/or demultiplexing a plurality of optical signals in the wavelength region and a signal conversion apparatus for interfacing a transmission line corresponding to any of the optical signals with the wavelength multiplexing apparatus. By using these apparatus according to the invention, the signal to be a reference for synchronization between the wavelength multiplexing apparatus and the signal conversion apparatus is reliably delivered via an existing optical transmission line therebetween, without the reduction of transmission quality and the limitation on modulation systems. Therefore, in an optical transmission system with the present invention applied thereto, it is possible to meet conditions for office establishment and arrangement of the apparatus and satisfy the demands for maintenance/operation flexibly and at a low cost. Further, service quality and reliability are maintained at high levels.

Wavelength multiplexing apparatus and signal conversion apparatus

An apparatus having n-number of working cross-connects for cross-connecting an n-bit input signals arriving from a plurality of input paths on a per-bit basis; n-number of first logic circuits for calculating the exclusive-ORs of each said n-bit and applying outputs to a standby cross-connect for providing outputs; n-number of second logic circuits for calculating the exclusive-ORs of said output signals from each of said working cross-connects and from the single standby cross-connect; and third logic circuits for selecting output signals of said working cross-connects and outputs of the second logic circuits. The apparatus detects the occurrence of an abnormality in working cross-connects by monitoring the outputs of the second logic circuits, identifies the faulty cross-connect by successively turning off one of the n-inputs to the first and second logic circuits, and select outputs from the second logic circuits instead of from the faulty cross-connect by using the third logic circuits.

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Kawasaki, Japan

Kazuhiro Kunimatsu