Fujitsu Corporation

Jun Wakabayashi

Masaaki Iwasaki

Masakazu Bamba

Tsutomu Chikazawa

Seiji Nakazumi

Kazuhiko Shiba

An optical wavelength path rearranging method includes detecting time that elapses since a setting of optical wavelength paths in an optical wavelength division multiplexing network; and moving to a predetermined long-period optical wavelength range, an optical wavelength path that is among the optical wavelength paths and for which the detected elapsed time is long, where the optical wavelength path rearranging method is executed by a processor.

Optical wavelength path rearranging method, computer product, optical transmission managing apparatus, and optical transmission apparatus

The communication method and the subsidiary transmission apparatus for a point-to-multipoint communication system in which the subsidiary transmission apparatus autonomously establishes point-to-multipoint communication between one main transmission apparatus and multiple subsidiary transmission apparatuses, without manually operating switches of the subsidiary transmission apparatuses. The subsidiary transmission apparatus generates, during the absence of a transmission request to the main transmission apparatus, an alarm signal to be transmitted to the main transmission apparatus through an upstream line, and the main transmission apparatus sends, while receiving the alarm signal through the upstream line, a specified notification signal, which is to be sent out in response to the reception of the alarm signal, to a downstream line, and the subsidiary transmission apparatus evaluates the state of use of the upstream line depending on the presence or absence of reception of the notification signal from the downstream line.

Communication method for point-to-multipoint communication system and subsidiary transmission apparatus for the same system

A clock regeneration apparatus which regenerates and distributes a timing signal in a synchronous data transmission network. The network is organized by a plurality of transmission units being linked in a ring topology, and at least two transmission units have external clock sources for synchronization purposes. The clock regeneration apparatus, disposed in each transmission unit, has a clock source list that contains entries for at least two line clock sources provided from neighboring transmission units. A clock selection controller selects a reference clock source with which the transmission unit is to be synchronized. A clock quality transmitter supplies one of the two neighboring transmission units that is not selected as the reference clock source by the clock source selection controller, with a message requesting not to use a corresponding line clock source for synchronization. This message transmission occurs only when the transmission unit is configured as a slave unit, and when the clock quality messages received from the neighboring transmission units exhibit equal clock quality levels continually for a predetermined period.

Clock regeneration apparatus for synchronous data transmission

A communication device includes a time switch array unit which performs a switching of transmission lines. A switch unit performs a switching connection from a protection channel line among the transmission lines to a working channel line, for each channel formed in the transmission lines. A bridge unit performs a switching connection from a working channel line among the transmission lines to a protection channel line, for each channel formed in the transmission lines. A control unit performs a recovery of a signal transmission on the working channel lines by controlling the switching connections of the switch unit and the bridge unit.

Growing community of inventors

Kawasaki, Japan

Jun Wakabayashi