Multiplex communications – Fault recovery – Bypass an inoperative station
Reexamination Certificate
1997-09-17
2001-09-18
Kizou, Hassan (Department: 2738)
Multiplex communications
Fault recovery
Bypass an inoperative station
C359S199200, C359S199200
Reexamination Certificate
active
06292464
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Related Case(s)
This application is related to Attorney Docket No. RR2092 entitled “APPARATUS AND METHOD FOR RESTORING FIBER OPTIC COMMUNICATIONS NETWORK CONNECTIONS” filed on Jul. 11, 1997, Ser. No. 08/893,433 which is hereby incorporated by reference.
2. Field of the Invention
The present invention relates generally to communications systems and specifically to fault tolerant fiber optic communication networks.
DESCRIPTION OF THE RELATED ART
Fiber optic communication systems are traditionally deployed in a point-to-point terminal configuration along a single path. A problem occurs if the connection path is somehow interrupted either due to equipment failure or a physical disruption in the connection.
Self healing ring architectures may be a solution that protects against service disruption and node failure along a given primary path. Referring to
FIG. 1
, a ring architecture is presented. If a message to be transmitted from node
150
to node
130
clockwise along path A-B cannot be completed due to a failure in path B, then the message is routed counter-clockwise along alternate path D-C. In fact, in this architecture messages from node
120
intended for any node are also routed counter-clockwise to the intended destination node.
Drawbacks to the above system include the requirement for having expensive add/drop multiplexers and associated support equipment present in each node.
Most installed networks are point-to-point systems and balancing traffic around a ring can be difficult. Further, managing an all-ring network and provisioning demands across several interconnected rings is more difficult and expensive than in a point to point network.
There is a need for a fast and reliable trigger and control mechanism. Any control signal supplied from a central control point or via standard communication channels such as DCC or X.25 will be inherently too slow to achieve desired restoration speeds.
There is accordingly a need for a new method and apparatus for inexpensively and easily rerouting traffic between nodes in a communication network when a given path becomes unusable in order to solve or ameliorate one or more of the above-described problems.
SUMMARY OF THE INVENTION
According to a preferred embodiment of the present invention, a system and method for connecting traffic along a fiber optic communications network is accomplished by automatically rerouting traffic upon the detection of a fault condition along a primary connection path.
The above method and apparatus utilize the functionality of a laser-diode transmitter which is uniquely tagged. Each laser diode transmitter transmits a specific bit pattern header unique at the beginning of a predetermined transmission sequence. Such a predetermined sequence may be a packet, the data tag associated with the power-up condition of the transmitter or other periodic or aperiodic data sequence. The network recognizes the unique identifier and configures the network to route all traffic from the identified transmitter along a specific path to its intended destination.
Fiber optic transmissions operate over fiber in one direction between first and second optical switches at a first wavelength &lgr;
1
and in the reverse direction at a second wavelength &lgr;
2
. A fault condition such as a broken fiber optic cable is detected at the optical switches when the previously transmitted signals are no longer received at either switch. Upon detection of the fault, the transmission of wavelength &lgr;
1
is automatically re-routed based on predetermined routing information stored in table look-up format associated with each switch.
The specific unique bit pattern associated with the laser transmitter of the transmission is identified by the switch at its input port, re-routed and connected to the appropriate output port for transmission along an alternate or redundant fiber path to its destination.
The re-routing of the return transmission at wavelength &lgr;
2
is done in an analogous manner.
The present invention is additionally applicable in restoring mesh or ring configurations and protects against single fiber or single equipment failures.
The foregoing features together with certain other features described hereinafter enable the overall system to have properties differing not just by a matter of degree from any related art, but offering an order of magnitude more efficient use of processing time and resources.
Additional features and advantages of the invention will be set forth in part in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The advantages of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the appended claims.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed.
The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate preferred embodiments of the apparatus and method according to the invention and, together with the description, serve to explain the principles of the invention.
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patent: 5751696 (1998-05-01), Bechtel et al.
patent: 5754789 (1998-05-01), Nowatzyk et al.
patent: 5903370 (1999-05-01), Johnson
patent: 6005694 (1999-12-01), Liu
Akhtar Shahid
Elahmadi Siraj Nour
Haynes and Boone LLP
Kizou Hassan
Nortel Networks Limited
Pezzlo John
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