Telefonaktiebolaget Lm Ericsson (publ)

Gpt Limited

Nigel Robert Wood

Bengt Johansson

Lars Egnell

Magnus G Öberg

Magnus &Ouml;berg

Robert Batchellor

Peter T Johnson

Jonas Hemgren

Tomas Askinger

An optical network comprises a bidirectional link connecting two nodes () through two optical fibers (). Optical output signals from optical transmitters () in a node are provided to transponders () issuing optical signals of well-defined wavelengths to a power combiner (), from which optical signals are forwarded to the other node on the respective fiber. The network can have protection for failures of various components. Thus, a spare transponder () can receive the optical output signals of an optical transmitter () in the case of a failure of an ordinary transponder (). The spare transponder () is also connected to the combiner (). The optical transmitters () and receivers () can be duplicated by providing spare transmitters (') and spare receivers (&#x2032;). Various arrangements can be used for connecting the output of a transmitter to an ordinary transponder or the spare transponder. For example, cross-bar switches () can be arranged at the outputs of a pair of an ordinary transmitter and a spare transmitter and at the inputs of a pair of an ordinary receiver and a spare receiver. For a node having N&#x2212;1 ordinary transmitters a N:1 switch () is then arranged at the input of the spare transponder ().

Protection of WDM-channels

The present invention relates to a self-healing ring network and a method for fault handling in said network. Said network comprises two communication paths ( ) and at least two nodes (N , N , N , N , N ). A first node (N ) and a second node (N ) suppress transmission to and/or reception from a segment (IS) in the ring, called an inactive segment. In the case of an occurring fault, the inactive segment is moved to the fault. According to the invention the network comprises a separate supervisory channel (OSC) for transmitting information of the fault between the nodes (N , N , N , N , N ) of the network, in which supervisory channel (OSC) a fault flag (ASSERT_PSS) is provided for the indication of the fault.

Self-healing ring network and a method for fault detection and rectifying

An optical fiber network of WDM type comprises two fibers which carry light signals propagating in opposite directions and which are arranged in a ring configuration. One standby link between two neighboring nodes is inactive but is made active if an active link fails. An add and drop node used in the network has band blocking filters connected in a fiber between a drop coupler and an add coupler, taking out a share of the light power in each direction to be received through bandpass filters in receivers and adding new wavelength channels produced in transmitters, respectively. Switches are used for receiving and transmitting on the wavelength channels in correct directions. The positions of the switches can be changed when the inactive link has to become one of the two active links directly connected to the node. A very efficient use of the wavelength channels in the network can then be achieved for nodes having a minimum of in-line components, and particularly, a minimum of in-line filtering components.

Optical WDM network having an efficient use of wavelengths and a node therefor

For use in a coherent optic switch a coherent optical transceiver has a single coherent receiver for both data recovery and to lock the transmitter to an optical reference input to the receiver. The switch may include polarisation control of the optical input to the receiver and wave division multiplex control of the transmitter frequency. The transmitter and receiver may be constructed as opto-electronic integrated circuits.

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Northants, United Kingdom

Nigel Robert Wood