An automatic frequency control system, for an optical coherent communication system, in which the frequency of local oscillation light 5 from a coherent light communication receiver 100 is swept to pull the intermediate frequency to a stable AFC point. The AFC is caused to operate with an intermediate frequency in the AFC operation range, and interrupted. Subsequently while sweeping the frequency of local oscillation light 5 in a certain direction in a predetermined range, the output voltage of ...

In a communications network where first and second nodes are interconnected by communication links, a source node transmits a path setup message for requesting a traffic path to a destination node. Each of the first and second nodes includes routing control means for establishing first and second transport paths on a first fault recovery layer between the first and second nodes. The first node further includes a database for storing identities of the first and second paths as a single virtual li...

A source node of a network transmits a path setup message for requesting a traffic path to a destination node. First and second nodes, located between the source and destination nodes, establishes first and second parallel transport paths on a first fault recovery layer between them. The first node further includes a database for storing identities of the first and second paths as a single virtual link as viewed from the source node. The first node responds to the path setup message for accommod...

To prevent load of route calculation from being centralized in part of units. A node calculates routes of a primary path and an alternate path and sends them to a management center. The management center checks whether SRLGs of the two routes overlap, and instructs the node to perform calculation again if the routes overlap. The management center searches for an alternate path having a route overlapping the route of the above described alternate path. When an overlapping alternate path exists, a...

Disclosed are a datalink system, which has: a data transmission system which is composed of a parallel-to-serial converter which converts a parallel signal into a serial signal, a data transmission line which transmits the serial signal output from the parallel-to-serial converter and a serial-to-parallel converter which converts the serial signal transmitted through the data transmission line into the parallel signal; and a control signal transmission system which is composed of a control signa...

In a communications network where multiple shared risk link groups are formed by links having a common risk, unreserved bandwidths are defined corresponding to all SRLG's and a maximum bandwidth of each link is set as an initial value of each of the defined unreserved bandwidths when a working path or a protection path of "1+1" or "1:1" recovery type is requested. When a protection path of "shared" recovery type is requested, unreserved bandwidths are defined corresponding to the SRLG's to which...

A parallel signal of a k bit width is converted such that every m bits of width is made a byte. It is then coded by a plurality i of encoders into a t byte error correcting code in which a byte length is of m bits and a code length is of 1 bytes. The coded parallel signal is interleaved by an interleaver and is distributed into a plurality 1 of transmitters. Each transmitter converts the parallel signal of an mi bit width into a serial signal and transmits the converted signal. Each receiver con...

A hierarchized path setting system in a communication network efficiently contains lower order paths in higher order path. The communication network has a plurality of nodes capable to perform switching process and demultiplexing process not only for lower order paths in a predetermined hierarchical level among hierarchized paths but also for higher order paths in a hierarchical level higher than the predetermined hierarchical level, and a plurality of links connecting these nodes. The system is...

An optical wavelength selector is provided that selects WDM channels from WDM optical signal and outputs each WDM channels from a plurality of ports. WDM optical signal in which m.times.n WDM channels are multiplexed is divided into n WDM channel groups and outputted by means of one wavelength-division demultiplexer. One WDM channel group is selected from the n WDM channel groups by means of n optical gate switches. The selected WDM optical signal is then separated into m WDM channels by wavelen...

This invention provides an optical path fault recovery method by which an end point node of an active path having received fault notification issues a resource securing request message transferred hop by hop to a start point node along the standby path. In the case where resources of the standby path are secured, when the resources are used by the extra traffic, the nodes on the standby path and the start point node that have received the message release the extra traffic and then secure the res...