Multiplex communications – Fault recovery – Bypass an inoperative station
Reexamination Certificate
1998-09-10
2001-06-19
Kizou, Hassan (Department: 2662)
Multiplex communications
Fault recovery
Bypass an inoperative station
C370S222000, C370S224000, C370S225000, C370S226000, C370S227000, C370S228000, C359S199200, C359S199200, C359S199200
Reexamination Certificate
active
06249510
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to optical networks and more particularly relates to a signal protection feature for an optical ring network.
BACKGROUND OF THE INVENTION
Optical networks require a reliable transport mechanism to transport information between optical nodes (switches) forming a bi-directional ring network. A reliable transport mechanism typically includes diverse transport paths to deliver information signals from one optical node to another optical node. The optical nodes forming the ring network transmit information over the shortest path to an intended recipient. However, if the transmission path fails, then the node will re-transmit the information over the other diverse path to the intended recipient. In this sense, one path provides protection for the other path when a failure occurs.
SUMMARY OF THE INVENTION
I have recognized that such a protection scheme is very expensive to implement in a so-called two fiber Bi-directional Line Switched Ring (BLSR) network arranged in accordance with the well-known Synchronous Optical NETwork (SONET) standard.
Specifically, for a particular optical transmission capacity, e.g., an OC48 optical system, channels 1 through 24 in each direction of a two fiber BLSR are reserved for service and channels 25 through 48 are reserved for protection. Thus, if the fiber carrying the in-service channels fails in one direction, then the transmitting node has to transfer the information from those service channels to the protection channels carried by the other fiber or path. In an optical transport system channels correspond to respective wavelengths, and the transfer would entail converting the wavelengths of the signals of the corresponding service channels to the wavelengths carried in the protection channels. For example, for a 48 channel system, the wavelengths of the signals being carried in channels 1 through 24 (i.e., &lgr;
1
through &lgr;
24
) would have to be respectively converted to the wavelengths carried in channels 25 through 48 (i.e., &lgr;
25
through &lgr;
48
) of the protection path. The equipment needed to perform such converting is indeed expensive, and would have to be provisioned at each node of a two fiber BLSR network.
I have further recognized that the foregoing problem may be dealt with at the optical level in an optical ring network by providing a one-to-one correspondence between the service channels that are transported over one fiber and the protection channels that are carried in the opposite direction over the other fiber of a two fiber BLSR network.
These and other aspects of the instant invention will become more apparent from the following detailed description and accompanying drawings.
REFERENCES:
patent: 5058105 (1991-10-01), Mansour et al.
patent: 5146452 (1992-09-01), Pekarske
patent: 5159595 (1992-10-01), Flanagan et al.
patent: 5818816 (1998-10-01), Chikazawa et al.
Kizou Hassan
Lucent Technologies - Inc.
Mendelsohn Steve
Tran Thien D
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