Fujitsu Corporation

Nobuyuki Nemoto

Kazuo Tanaka

Taro Asao

Kazunori Horachi

Hideo Sunaga

Toshihiro Suzuki

Manabu Suzuki

Kazuo Takatsu

Yoshinori Nakamura

Junichi Ishiwatari

Akihiko Oka

Takashi Umegaki

Miwa Taniguchi

Hiroaki Mori

Nobuo Iguchi

Toshiharu Sakai

Hiroyuki Matsumoto

Masaki Kubo

Masaru Kameda

Toshikazu Ota

Miki Hagino

Shigeyuki Kobayashi

Shuniti Nakayama

A wavelength dispersion compensation control method determining whether a clock component is contained in an optical signal received from an optical transmission path and, if a clock component if contained in the optical signal, extracting the clock component, and stopping control of a variable wavelength dispersion compensator when no clock component is extracted.

Wavelength dispersion compensation control method and wavelength dispersion compensation control device

In each node of an optical transmission system: an optical preamplifier has an ALC function for maintaining an optical output level constant and an AGC function for maintaining the gain constant; the operational mode of the optical preamplifier is changed from an ALC mode to an AGC mode after the gain is set in the ALC mode; an optical postamplifier has an AGC function; an optical switch unit performs an optical crossconnect operation; and a thru-light-shutoff control unit makes a switch setting so as to shut off pass-through light in the optical switch unit and stop transmission of an optical signal having an unstable level to a next stage when the optical preamplifier operates in the ALC mode, and clears the switch setting when the operational mode of the optical preamplifier is changed to the AGC mode.

Optical transmission system

A WDM optical transmission apparatus is disclosed utilizing ASE light. The WDM optical transmission apparatus includes a pre-amplifier having two control modes consisting of ALC mode in which the gain of an optical amplifier is controlled such that the total output of the optical amplifier is constant for a multiplexed wavelength number n, and of AGC mode which is a control mode maintaining constant the ratio of an optical input level to an optical output level for the multiplexed wavelength number n; and a post-amplifier having two control modes consisting of ASE mode in which the gain of the post-amplifier is set higher than that in the AGC mode and is set such that the output level of ASE light corresponds to the multiplexed wavelength number n, and of the AGC mode; wherein in the ASE mode, the gain of the pre-amplifier in the WDM optical transmission apparatus at the next node is set under an ALC control utilizing ASE light output from the post-amplifier.

Pre-amplifier gain setting method utilizing ASE light and WDM optical transmission apparatus employing the method

The gain control circuit controls the amplification ratio of EDFA based on the results of having measured the input power monitor which monitors the EDFA input optical level which amplifies light and of having measured the output power monitor which monitors the output optical level. The optical pre-amplifier receives a notice of the number of wavelengths from a fore node and a notice of whether the optical post-amplifier of a fore node is in normal operation by a supervisory control signal, and changes over the gain control circuit to either the ALC or AGC mode. When the number of wavelengths changes while the optical pre-amplifier is operating in the ALC mode, the optical pre-amplifier is controlled in the AGC mode using the backed-up amplifier gain. Also, the gain value when the optical pre-amplifier is in routine operation is backed up in an amplifier gain back-up unit and an back-up unit.

Optical amplifier supervisory control method in WDM communication system

Disclosed are a signal control apparatus, a transmission system and a signal resynchronization control method, which efficiently prevent the occurrence of slipping and execute high-quality signal resynchronization control. The signal control apparatus comprises a serial/parallel converting section, a window setting section and a parallel/serial converting section. The serial/parallel converting section performs serial/parallel conversion on an input signal to yield parallel data. The window setting section sets a small window having a readout guarantee area narrowed at an optimal position at the time of reading the parallel data when an operational state is unstable, and sets a large window having the readout guarantee area widened from the optimal position when the operational state is stable. The parallel/serial converting section reads the parallel data based on a read pulse positioned within the readout guarantee area corresponding to the small window or the large window, and performs parallel/serial conversion on the parallel data to yield serial data. The transmission system comprises a plurality of transmission apparatuses each including the above signal control apparatus, and a transmission medium for connecting the transmission apparatuses. The signal resynchronization control method executes signal resynchronization control by performing the functions of the individual sections of the signal control apparatus.

Signal control apparatus, transmission system and signal resynchronization control method

An apparatus for resynchronizing data signals by using dual port data buffer storage, which prevents data corruption and subsequent system disruption from happening by employing a mechanism to keep an adequate distance between read and write address pointers. An input unit receives an incoming data stream having a cyclic data structure of N bytes. A data writing unit sequentially writes each data word of the received data stream into a storage unit with a capacity of 2N bytes in synchronization with a first clock. A data reading unit sequentially reads out each data word from the storage unit in synchronization with a second clock. A detection unit tests whether the write and read address pointers have come within a predetermined threshold distance. A relocation unit moves the read address pointer by N bytes to increase the distance between the read and write address pointers, when the detection unit has detected that the write and read address pointers have come within the threshold distance. An outputting unit transmits to an external destination the data words read out by the data reading unit.

Signal resynchronization apparatus having capability to avoid data corruption

An alarm detection apparatus includes a plurality of alarm detectors detecting and/or cancelling alarms for identical and different error rates. The plurality of alarm detectors are grouped into a major detector unit made up of alarm detectors which detect major error rates, and a minor detector unit made up of alarm detectors which detect minor error rates. The major detector unit and the minor detector unit output detection outputs corresponding to specified detection rates thereof. A predetermined alarm detector corresponding to a part of the minor detector unit has a specified detection rate overlapping a specified detection rate of the major detector unit being controlled, so that a detection function or a detection output of the predetermined alarm detector is disabled.

Alarm detection apparatus

In a signal processing circuit capable of handling different signal rates, an STS-3 signal input as 78 M.times.2 parallel signals is converted by a serial-to-parallel converter into 19 M.times.8 parallel signals, thus making the number of signal lines equal to that of an STS-12 signal input as 78 M.times.8 parallel signals. Depending on whether the mode is STS-12 mode or STS-3 mode, a first selector selects the 78 M.times.8 parallel signals of STS-12 or the 19 M.times.8 parallel signals of STS-3, and supplies the selected signals to a signal processor. Depending on whether the mode is STS-12 mode or STS-3 mode, a second selector selects a 78-M clock or a 19-M clock and supplies the selected clock to the signal processor.

Signal processing apparatus capable of processing received signals of

An optical terminal system having self-monitoring function is disclosed, which includes a high-level group loopback section for internally looping back a serial electric signal, a low-level group loopback section for internally looping back a parallel electric signal, a self-loop section for connecting a receiver device and a transmitter device to loop an electric signal received by the receiver device directly to the transmitter device, and a self-monitoring controller for performing a self-monitoring test on respective components of the receiver device and transmitter device by using the self-loop section and either one of the high-level group loopback section and the low-level group loopback section. The optical terminal system can selfcheck the functions thereof through self-monitoring without depending on a network.

Optical terminal system having self-monitoring function

A redundantly constructed protection channel access transmission apparatus includes current units and spare units by which protection channel access data can be transmitted even if any one of the current units or spare units is in an alarm state. In a normal state, the current units transmit work data and the spare units transmit the protection channel access data. When any one of the current units is in an alarm state, a selector selects work data and supplies the work data to a secondary spare unit. Then, the secondary spare unit performs a signal processing in place of the current unit. On the other hand, when any one of the spare units is in an alarm state, the selector also selects protection channel access data in the same way and the secondary spare unit performs a signal processing in place of the spare unit. With this arrangement, even if any one of the current units or spare units is in an alarm state, the secondary spare unit is selected and processes the signal of the current unit or spare unit in the alarm state, whereby both of the work data and protection channel access data can be transmitted as they are.

Growing community of inventors

Kawasaki, Japan

Nobuyuki Nemoto