Optical: systems and elements – Deflection using a moving element – Using a periodically moving element
Reexamination Certificate
1999-12-23
2003-03-04
Negash, Kinfe-Michael (Department: 2633)
Optical: systems and elements
Deflection using a moving element
Using a periodically moving element
C359S199200
Reexamination Certificate
active
06529298
ABSTRACT:
FIELD OF THE INVENTION
This invention relates generally to optical ring networks and more particularly to a method of deactivating working fiber resources in optical ring networks.
BACKGROUND ART
Today's optical transport networks employ a number of different topologies to satisfy increasing demands for network simplicity, cost containment, bandwidth efficiency and survivability. Common network topologies include point-to-point terminal configurations, linear add/drop multiplexer configurations and ring configurations. Of all these different topologies, ring configurations are often the preferred network configuration for applications requiring high transport capacity.
In optical ring networks, the bandwidth available in each fiber interconnecting nodes can be allocated in various ways to meet different capacity demands. In some ring configurations, the bandwidth available for transport can be provisioned as a single optical transmission path. However, in the vast majority of ring configurations, the bandwidth is partitioned into channels or wavelengths to increase capacity.
In optical ring networks as in other optical configurations, it is common to use the term fiber generally to denote traffic carrying capacity. As such, in addition to denote physical fibers, the term fiber can also be used to denote single channels or wavelengths in a physical fiber. For clarity and unless stated otherwise, the term fiber as applied generally to optical networks is hereinafter used to denote both a physical fiber and a single channel or wavelength within a physical fiber.
In addition to providing large capacity, optical ring systems are also designed with redundant equipment to have other attributes such as, for example, bidirectionality and/or increased reliability to reduce service failures. In conventional unidirectional and bidirectional ring systems for example, multiple fibers are commonly installed to achieve transmit and receive operations. Additional fibers are also installed to “protect” the working fibers in the event of a link (span) failure. Current ring protection schemes include dedicated protection, 1 protection fiber for each fiber or 1:1 protection which can be used in both path switched and line switched configurations.
In optical ring networks, some spans that interconnect nodes are not required to carry working traffic. This is either because there is no requirement for traffic or because there is too much capacity available and it cannot all be efficiently used. This is particularly true for dense wavelength division multiplex (DWDM) systems where the number of channels or wavelengths available on some spans can very well exceed the transport capacity required.
Currently, all spans separating adjacent nodes in a ring configuration have to be fiber equipped because of the protection usage that is necessary on a ring configuration. However, this requirement only makes use of protection fibers. On spans where traffic is low or non-existent, the working fibers present may never be used. As a result, the fiber capacity available in some optical ring networks may be underutilized. This is particularly true for long distance networks or continental networks where traffic is largely concentrated on East-West spans and little if any traffic is transmitted along North-South spans. In these networks, the fiber capacity on North-South spans is not efficiently utilized and in many instances may not be needed for traffic carrying purposes.
In addition to this ineffective use of fibers, the accommodation of multiple fibers between nodes necessitates at each node the installation of connection equipment for each fiber. However, duplicating this equipment for each fiber may also prove to have a considerable impact on the system cost, particularly on spans where the fiber capacity is underutilized.
Therefore, it would be desirable to use the existing working fiber capacity more efficiently in optical ring networks or alternatively deactivate underutilized fibers and associated equipment so that they can be removed or re-provisioned for use in other network configurations.
SUMMARY OF THE INVENTION
The present invention provides a method of deactivating working fiber resources in an existing optical ring network or system for a cost-effective and efficient allocation of the fiber resources available in the ring network. The invention can be applied to deactivate physical working fibers as well as working channels or wavelengths provisioned on a physical working fiber. The term fiber is therefore used to denote both a physical fiber and a channel or wavelength provisioned on a physical fiber.
According to the invention, when a working fiber between any two nodes in an existing ring network is underutilized, the traffic scheduled for transmission thereon is re-routed around the network away from the fiber. As a result, the fiber and associated connecting equipment thus become unused and unnecessary for traffic carrying purposes and can then be deactivated.
Advantageously, the present invention eliminates the need for working fibers and associated optics equipment on spans where traffic is low or non-existent and can provide fiber and equipment capacity savings of up to fifty percent on each span while retaining full protection usage. According to the invention, the unused fibers and equipment can be removed or alternatively be re-provisioned to provide a cost-effective and efficient allocation of the resources available in the network.
Other aspects and features of the present invention will become apparent to those ordinarily skilled in the art upon review of the following description of specific embodiments of the invention in conjunction with the accompanying figures.
REFERENCES:
patent: 5717796 (1998-02-01), Clendening
patent: 5903370 (1999-05-01), Johnson
patent: 6046832 (2000-04-01), Fishman
patent: 6052210 (2000-04-01), Nathan
patent: 6222653 (2001-04-01), Asahi
patent: 6295146 (2001-09-01), Nathan et al.
Caporuscio Robert
Charron Paul
Deboer Evert E.
Leung Johnny
Olajubu Joseph
Negash Kinfe-Michael
Nortel Networks Limited
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