Redundant add/drop multiplexor

#The present invention relates to telecommunications in general, and, more particularly, to an architecture for a composite add/drop multiplexor, which is commonly used in high-speed backbone networks (e.g., SONET/SDH networks, etc.).

#The first generation of optical fiber systems in the public telephone network used proprietary architectures, equipment line codes, multiplexing formats, and maintenance procedures. This diversity complicated the task of the regional Bell operating companies (“RBOCs”)and the interexchange carriers (e.g., AT&T, Spring, MCI, etc.) who needed to interface their equipment with these diverse systems.

#To ease this task, Bellcore initiated an effort to establish a standard for connecting one optical fiber system to another. That standard is officially named the Synchronous Optical Network, but it is more commonly called “SONET.” The international version of the domestic SONET standard is officially named the Synchronous Digital Hierarchy, but it is more commonly called “SDH.”

#FIG. 1 depicts a block diagram of the illustrative embodiment of the present invention.

#FIG. 2 depicts a block diagram of node 101-i, as shown in FIG. 1.

#FIG. 3 depicts a block diagram of switch complex 201, as shown in FIG. 2.

#FIG. 1 depicts a block diagram of the illustrative embodiment of the present invention, telecommunications network 100, which is a SONET/SDH ring network operating as a bi-directional line switched ring (“BLSR”). In accordance with the illustrative embodiment, telecommunications network 100 comprises four nodes, nodes 101-1 through 101-4, that are interconnected by two sets of optical fibers, each of which carries a SONET/SDH OC-768 signal. Therefore, each node comprises two OC-768 line inputs and two OC-768 line outputs.

#Although the illustrative embodiment uses the SONET/SDH protocol, it will be clear to those skilled in the art, after reading this disclosure, how to make and use embodiments of the present invention that use other protocols, such as dense wavelength division multiplexing (“DWDM”). Although the illustrative embodiment is a ring network, it will be clear to those skilled in the art, after reading this disclosure, how to make and use embodiments of the present invention in which some or all of the nodes are interconnected in a mesh or non-ring topology. Although the illustrative embodiment operates as a bi-directional line switched ring, it will be clear to those skilled in the art, after reading this disclosure, how to make and use embodiments of the present invention that operate in a different fashion (e.g., as a unidirectional path switched ring, as a four-fiber ring, etc.). Although the illustrative embodiment comprises four nodes, it will be clear to those skilled in the art, after reading this disclosure, how to make and use embodiments of the present invention that comprise a different number of nodes. Although the illustrative embodiment carries OC-768 SONET/SDH frames, it will be clear to those skilled in the art, after reading this disclosure, how to make and use embodiments of the present invention that carry other SONET/SDH rate frames.

#As shown in FIG. 1, node 101-i, for i=1 to 4, is capable of receiving sixteen (16) OC-192 tributaries on tributary bus 121-i, and of spawning sixteen (16) OC-192 tributaries on tributary bus 122-i. Although each node in the illustrative embodiment comprises the same number of tributaries, it will be clear to those skilled in the art, after reading this disclosure, how to make and use embodiments of the present invention in which some or all of the nodes have a different number of tributaries. Although each tributary operates at an OC-192 data rate, it will be clear to those skilled in the art, after reading this disclosure, how to make and use embodiments of the present invention in which some of the tributaries have a different data rate (e.g., OC-48, OC-12, OC-3, etc.). Although each node is capable of receiving sixteen (16) tributaries, it will be clear to those skilled in the art, after reading this disclosure, how to make and use embodiments of the present invention in which some or all of the nodes are capable of receiving a different number of tributaries. Although each node is capable of spawning sixteen (16) tributaries, it will be clear to those skilled in the art, after reading this disclosure, how to make and use embodiments of the present invention in which some or all of the nodes are capable of spawning a different number of tributaries.