Optical: systems and elements – Deflection using a moving element – Using a periodically moving element
Patent
1998-05-27
2000-07-11
Chan, Jason
Optical: systems and elements
Deflection using a moving element
Using a periodically moving element
359110, 359117, 359128, 359166, 370222, 370223, H04B 1008, H04J 1400, H04J 1402, G01R 3108
Patent
active
060881410
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD FOR THE INVENTION
The present invention relates to an apparatus and a method for a communication network, more particular to a self-healing network.
DESCRIPTION OF RELATED ART
In a conventional self-healing ring architecture, synchronous digital hierarchy SDH or synchronous optical network SONET, utilizing add/drop multiplexer (ADM), the optical fiber is only used as point to point link and optical-electrical conversion is operated at each node. In such a ring the bottleneck is constituted by the speed of the processing electronics, and the bandwidth-sharing is characteristic for this architecture leads to a limitation of the network capacity.
In the article "Self-Healing Ring Network Architecture Using WDM for Growth", ECOC 92, Tu P1.16, by Aly Elrefaie, is presented a self-healing ring network. It is described by a 2-fiber WDM ring network where N-1 local offices are originating traffic that is served by a single hub. Transmission on both fiber rings is identical except for the direction of propagation; the counter propagating signals facilitate the network survivability during a cable cut. Each of the N-1 local offices is assigned a unique wavelength for transmission to and receiving from the hub.
In the PCT-application WO 93/00756, by Sandesara is described a self-healing bidirectional logical-ring network using crossconnects nodes. The network is partitioned into independent segments. Each segment consists of two or more nodes, interconnected with two transmission links working in different directions. When a failure occurs a crossconnect maintains a pre-selected pattern of interconnections between segments.
In the above PCT-application WO 93/00756 is described a unidirectional self-healing network. In addition to the transmission link there is also a spare link. The transmitted signal is duplicated and flows in both said links at the same time. The destination node then selects the better of the two signals. It is also stated that the signal structure in previous known uni- and bidirectional networks consists of a predetermined number of subrate multiplexed channels operating at fixed rate.
SUMMARY
This invention pays attention to the problem that it takes long time between detecting a fault and re-routing the traffic in a communication network, in particular a self-healing ring network. This invention also addresses the problem that a tremendous amount of traffic and data might become lost when an error occurs and the traffic has to be re-routed in the communication network.
According to this invention, a communication node in a communication network can detect the fault easily and quickly, in that the detection takes place in the node itself. Furthermore, the node is able to detect a fault in the network that occurs in the immediate surrounding of this node. Upon detection of a fault the node is capable of swiftly re-routing any traffic and will, additionally, go from an active working state into a protection state. After error identification the node will self-heal, recuperate, and automatically go back into the working state
The purpose of the invention is to get a self-healing network in which the nodes are rapidly self-healing.
A further purpose is that the nodes need no network management for the healing.
An advantage is that the node can add/drop any of the wavelengths for the local traffic and by-pass others.
Another advantage is that if a cable is cut or broken all traffic can swiftly be re-routed by the node itself, restoration takes place within the node local control system, without involving network management.
Yet another advantage is that this invention shortens the time needed for the network to recover.
Further advantage is that network restoration is fast in order to provide high quality service.
The invention will be presented with the help of the best mode carrying out the invention characterized by the characterizing features set forth in the appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1a shows a communication network system.
FIG. 1b shows a
REFERENCES:
patent: 4829512 (1989-05-01), Nakai et al.
patent: 5081452 (1992-01-01), Cozic
patent: 5159595 (1992-10-01), Flanagan et al.
patent: 5457556 (1995-10-01), Shiragaki
patent: 5680235 (1997-10-01), Johansson
A. Elrefaie, "Self-Healing Ring Network Architecture Using WDM for Growth," ECOC 92, Tu P1.16.
Andreozzi Paolo
Merli Stefano
Norbiato Renato
Testa Francesco
Chan Jason
Sedighian Mohammad
Telefonaktiebolaget LM Ericsson
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