Optical WDM ring network

Details Optical WDM ring network Optical WDM ring network

1997-12-03

2001-02-27

Chan, Jason (Department: 2733)

Optical: systems and elements

Deflection using a moving element

Using a periodically moving element

C359S199200, C359S199200

Reexamination Certificate

active

06195186

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to an optical ring network, and in particular to a ring network having a protection capability using Wavelength-Division Multiplexing (WDM) technology.
2. Description of the Related Art
In an optical WDM ring network using a wavelength for services and another wavelength for protection, duplicate signals are generated by a node to travel over an optical fiber in opposite directions. In each node of the ring network, it is determined whether a signal can be received from another node on the wavelength for services. If a node receives the signal on the wavelength for services, the node selects the service wavelength to receive a transmission signal.
In case of a cable cut or a node failure occurring at a location, however, the node cannot receive the signal on the service wavelength from another node which is located between the failure location and the node in the downstream direction. In this case, the node selects the protection wavelength to receive the duplicate transmission signal traveling in the opposite direction. Therefore, data transmission can be performed as normal even if transmission failures occur. Such an optical WDM ring network has been disclosed in Japanese Patent Unexamined Publication No. 6-97950.
Other survivable WDM ring networks have been proposed by A. F. Elrefale (ICC'93 Geneva. 1993, Geneva, paper 48.7) and by R. E. Wagner et al. (OEC'94, 1994, Japan, 14C3-1).
However, the conventional ring network as described above has disadvantages in that the number of assigned wavelengths is twice that of nodes because a pair of wavelengths for service and protection are assigned to each node. This results in broadened necessary bandwidth. Further, a wavelength selector provided at each node has the increased number of wavelengths to be selected. Furthermore, since duplicate signals are traveling in opposite directions, a transmission line cannot be used effectively.
SUMMARY OF THE INVENTION
An object of the present invention is to provide an optical WDM ring network which can effectively use wavelength components thereof to achieve high performance.
Another object of the present invention is to provide an optical WDM ring network which can ensure reliable data transmission in case of line or node failures.
According to the present invention, in a ring network that includes a plurality of transmission media and a plurality of nodes coupled through the transmission media in ring topology, each of the nodes includes a transceiver for transmitting and receiving a plurality of signals and a switch for changing a path for each signal which is transmitted and received to and from one of the transmission media through the path.
Further, the present invention may be applied to a ring network including an even-number of optical fibers wherein each pair of optical fibers forms a bidirectional transmission line and a plurality of nodes coupled through the optical fibers in ring topology. In this ring system, each of the nodes includes the even-number of interfaces coupled to the optical fibers, respectively, and the even-number of optical transceivers each comprising an optical transmitter and an optical receiver, wherein each of the optical transmitter and the optical receiver is coupled to a selected one of the interfaces The node is further provided with a switch for changing a combination of an interface and each of the optical transmitter and the optical receivers
Since the switch can select one of the transmission media for transmitting or receiving each signal, all wavelength components in the ring network are usable for services without the need of setting wavelengths for protection. Therefore, the wavelength components can be used effectively, resulting in reduced wavelength band and the reduced number of wavelengths to be selected in each node.


REFERENCES:
patent: 5442623 (1995-08-01), Wu
patent: 5717796 (1998-02-01), Clendening
patent: 5923449 (1999-06-01), Doerr et al.
patent: 6023359 (2000-02-01), Asahi
patent: 6-97950 (1994-04-01), None
A.F. Elrefaie, “Multiwavelength Survivable Ring Network Architectures”, ICC Geneva, 48.7, May 23-26, 1993.
R.E. Wagner, et al., “Survivable WDM Rings for Interoffice Networks”, OEC'94, 1994, 12C3-1.

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