Abstract:
Method and apparatus for providing a communication link between support equipment in an optical network and an operation support system. In a first embodiment, dark bandwidth of the communication trunks is appropriated for use as a service channel. A master service node receives messages from the operation support system and places the messages in the dark bandwidth. Local service nodes, provided in an optical ring, monitor the dark bandwidth and route message either to support equipment at the node or to other local service nodes as appropriate. Multiplexors are provided at the master service node and local service nodes to interface between optical network elements and support equipment. A second embodiment provides a radio link between the operational support system and the service nodes of the optical network.

Description:
This application is a continuation of U.S. patent application Ser. No. 08/951,697 filed Oct. 16, 1997 now U.S. Pat. No. 6,072,611. 
    
    
     The present invention relates to telecommunications networks and, more particularly, to a method of providing operational support in a synchronous optical network. 
     Modern telecommunications networks are evolving. There is a shift from asynchronous communications networks to synchronous communications networks. The advent of optical transport as a transmission technique has given rise to a set of standards for a synchronous optical network (“SONET”) in the United States and in Europe. The United States standards are found in ANSI T1.105, ANSI T1.106 and ANSI T1.107; the European standards are found in the SDH standard established by ITU-T. In these optical networks, SONET network elements (“SNE&#39;s”) exchange data over interconnecting optical cable. Synchronization of each SNE is maintained by a timing signal generator (“TSG”) and related peripheral equipment. The TSG establishes a timing reference, either through GPS equipment incorporated into the TSG or by derivation from the SNE&#39;s optical transport. 
     Both SNE&#39;s and TSG&#39;s must be monitored, maintained and configured by a network administrator, such as a Operation Support System (“OSS”). Although the SONET standard dedicates bandwidth to provide for OSS messaging to the SNE&#39;s, no such accommodations are made for TSG&#39;s or the other peripheral equipment. 
     Accordingly there is a need in the art for a means for providing communication between a TSG and an OSS in a SONET network. 
     SUMMARY OF THE INVENTION 
     The disadvantages of the art are alleviated to a great extent by a communications system that provides a communication link between an operation support system and support equipment at the SONET network element. In a first embodiment, the invention exploits dark bandwidth in the SONET communication protocol to build a communication channel with the support equipment. In a second embodiment, the support equipment is provided with two way radio communication equipment to communicate messages between the operation support system and the support equipment. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a block diagram of a SONET ring suitable for use with the present invention. 
     FIG.  2 ( a ) is a block diagram of a local service node of the SONET ring constructed in accordance with the present invention; FIG.  2 ( b ) illustrates the operation of a local service node according to the present invention. 
     FIG.  3 ( a ) is a block diagram of a master service node of the SONET ring constructed in accordance with the present invention; FIG.  3 ( b ) illustrates the operation of the master service node according to the present invention. 
     FIG.  4 ( a ) is a block diagram of a second embodiment of the invention; FIG.  4 ( b ) illustrates the operation of the system of FIG.  4 ( a ). 
    
    
     DETAILED DESCRIPTION 
     FIG. 1 shows a communication system constructed in accordance with the present invention. A SONET ring is populated by a number of SNE&#39;s  100  interconnected by optical communication trunks. Each SNE  100  is provided with a TSG  150 . The TSG  150  provides a timing reference to its respective SNE. TSG&#39;s are configurable devices requiring support from the OSS  200  through signaling. The OSS  200  may interface with the SONET ring through a wide area network  250  (“WAN”), such as AT&amp;T&#39;s network service division network. The present invention provides a communication link from the OSS  200  to the TSG&#39;s  150 . 
     In the present invention, the SNE may be a SONET network element such as the FT2000 available from Lucent Technologies of Holmdel, N.J. The TSG may be a digital clock distributor such as the DCD523 available from Telecom Solutions of San Jose, Calif. 
     In a first embodiment, the OSS  200  communicates with the TSG&#39;s  150  in a SONET ring through an OSS  200  service channel created from dark bandwidth available in the SONET bitstream. A master service node (“MSN”) communicates with the OSS  200 , possibly via the WAN  250 . The master service node MSN relays messages from the OSS  200  to local service nodes (“LSN”) in a SONET ring and vice versa. Local service nodes in the SONET ring monitor the dark bandwidth for the presence of the OSS service channel. When a local service node detects the channel, it determines whether it is the addressee of the message. If so, the local service node keeps the message; otherwise the local service node LSN returns the message to the dark bandwidth and forwards the message to the next local service node in the ring. 
     Dark bandwidth represents bandwidth that is allocated for events that rarely arise. For example, the U.S. standard provides for two orderwire channels that are intended to be used during maintenance on site at one or more SNE&#39;s. The standard contemplates that traditional phone service may not be available at all SNE sites and, therefore, provides the orderwire channels so that the technicians may communicate with one another. Because such maintenance occurs infrequently, the present invention may use an orderwire channel to communicate with TSG&#39;s. 
     Other available dark bandwidth may be used as desired. The standards define other bandwidth that is not allocated currently to any application. As the standards evolve, some of this available bandwidth may be allocated to provide the service channel of the present invention. 
     FIG.  2 ( a ) illustrates the construction of a local service node LSN. A local service node is provided with a local multiplexor (“LMUX”)  120 . interconnecting the SNE  100  to the TSG  150 . The LMUX  120  is preprogrammed with an LSN address uniquely identifying the local service node. 
     The LMUX  120  is configured to monitor dark bandwidth input to the SNE  100  over fiber optic cable  105 , looking for an OSS service channel (FIG.  2 ( b ), Step  1000 ). When OSS signaling is detected, the LMUX  120  decodes the message to identify an addressee field in the message (Step  1010 ). The LMUX  120  compares the decoded addressee field against its own LSN address to determine whether the message is intended for its local service node or another (Step  1020 ). If the message is addressed to another local service node, the LMUX  120  routes the message on another fiber optic cable  110  for the next local service node in the SONET ring (Step  1030 ). If the message addresses the LMUX&#39;s own local service node, the LMUX routes the message to the TSG  150  (Step  1040 ). 
     The LMUX  120  may be a multiplexor model no. A18-05721-xx available from Dantel, Inc., 2991 North Argyle, Fresno, Calif. 93727. In the orderwire embodiment, the LMUX  120  interfaces with the SNE  100  over two orderwire ports provided on the SNE  100 . For example, inputs C 1  and C 2  of the Dantel multiplexor may interconnect directly to the East Line Orderwire (“ELOW”) and West Line Orderwire (“WLOW”) ports of the SNE over an RS-422 serial interface. The Dantel multiplexor in turn, interfaces with the COM1 port of the DCD-523 timing signal generator as a conventional RS-232 connection. 
     The OSS service channel will flow through the SONET ring in one direction, such as from east to west. Thus, OSS signaling may be input to the SNE  100  via the eastern port. The LMUX  120  monitors the ELOW port of the SNE  100  for the OSS service channel. When the LMUX  120  encounters service channel messages that address other local service nodes in the ring, the LMUX  120  routes the messages to the WLOW port of the SNE  100 . 
     The TSG  150  may be programmed to issue alerts when it encounters certain operating conditions. To alert the OSS  200 , a TSG  150  commands the LMUX  120  to signal the OSS  200  and provides information content of a message to be transmitted over the OSS service channel (Step  1050 ). The LMUX  120  prepares the message for transmission by including it in a message containing an author field (Step  1060 ). The author field identifies the originating local service node as the originator for the message. Typically, the LMUX  120  confirms that the incoming service channel is available (unoccupied) and places the message in the outgoing OSS service channel (Steps  1070  and  1080 ). 
     Steps  1070  and  1080  may be omitted when the LMUX  120  is the Dantel multiplexor. The Dantel multiplexor divides the dark bandwidth available for use as the service channel into sub-channels, each associated with one of the LSNs. In this embodiment, the messages addressed to and originating from each LSN are placed into an associated sub-channel. In this embodiment; because each sub-channel is associated with a specific one of the LSN&#39;s, no addressee or originator field is required in messaging to identify the LSN. 
     Local service nodes communicate with the OSS  200  via a master service node in the SONET ring. Shown in FIG. 3, the master service node includes a master service node multiplexor (“MMUX”)  220  and a switch box  240  that interconnect the SNE  100  to the WAN  250  or to the OSS  200 . The MMUX  220  and switch box  240  carry messages of the various local service nodes in logical channels. That is, software or hardware control within the MMUX  220  and switch box  240  isolate traffic of a first local service node from traffic of other local service nodes. 
     As in the local service nodes, the MMUX  220  monitors the dark bandwidth in which the OSS service channel may appear (FIG.  3 ( b ), Step  2000 ). When signaling is detected, the MMUX  220  decodes the messages to identify the author of the message (Step  2010 ) and places the message in the logical channel associated with the authoring local service node. The MMUX forwards the message to the switch box  240  (Step  2020 ). The switch box  240  feeds the messages into the WAN  250  for transport to the OSS  200  (Step  2030 ). 
     Messages transmitted from the WAN  250  to the master service node MSN intended for one of the local service nodes are received by the switch box  240 . The switch box  240  separates the messages received into the logical channels associated with the appropriate local service nodes (Step  2040 ). The switch box  240  outputs the content of the logical channels to the MMUX  220  (Step  2050 ). The MMUX  220  generates an addressee field for the message (Step  2060 ) and inserts the message into the OSS service channel (Step  2070 ). 
     The MMUX  220  may be, for example, model no. A18-05721-xx available from Dantel, Inc. The switch box  240  may be a DataKit II VCS also available from Lucent Technologies. In one embodiment, the switch box  240  and MMUX  220  have different wired connections for each logical channel. 
     A second embodiment of the present invention is shown in FIG.  4 ( a ). In this embodiment, each SNE operates as a local service node in communication with the OSS  200  via an RF communication link. The local service node is provided with a two way communicator  300  interconnected to the TSG  150 . The communicator  300  includes an RF transceiver  310 , such as a two-way pager, and a communicator processor  320 . The communicator  300  communicates with a base communicator  400  over the RF link. The base communicator  400  addresses each of the communicators  300  uniquely. The OSS  200  communicates with the base communicator  400  via the WAN  250 . 
     A method of operation of the second embodiment is shown in FIG.  4 ( b ). To signal the LSN, the OSS  200  provides the base communicator  400  with a message and an identifier of a communicator  300  to which the message should be delivered (Step  3000 ). The QSS  200  maintains a database that associates each TSG  150  with the respective communicator  300  to which it is attached. The OSS  200  refers to the database  260  each time it generates messages to a TSG  150  for communication over the RF link. 
     The base communicator  400  transmits messages to the communicator  300  (Step  3010 ). The RF transceiver  310  receives the message and converts it down to digital communication data according to procedures known in the art (Step  3020 ). The transceiver presents the message to the communicator processor  320  (Step  3030 ), who in turn formats the message and presents it to the TSG  150  (Step  3040 ). 
     For communication from the local service node to the OSS  200 , the TSG  150  formats a message and presents it to the communicator processor  320  to transmit the message to the OSS  200  (Step  3050 ). The communicator processor  320  formats the message according to any signaling protocol dictated by the RF link and causes the transceiver  310  to transmit the message. The transceiver broadcasts the message to the base communicator  400  (Step  3060 ). The broadcast identifies the communicator that broadcasts the message. 
     The base communicator receives the message and generates a digital signal therefrom (Step  3070 ). The base communicator then signals the OSS  200 , presenting the message and identifying the communicator that originated it (Step  3080 ). 
     The transceiver  310  may be, for example, a conventional alpha numeric two way pager such as the REFLEX pager commercially available from Motorola, Inc. of Schaumburg, Ill. In this embodiment, the basic communicator may be a commercial paging service. The database  260  stores pager identification numbers associating pagers with each TSG  150 . The OSS  200  interfaces with the pager service  400  according to conventional procedures to transmit messages using the pager system. 
     In the embodiment of FIG.  4 ( a ), it may be desirable to enhance security of the system by encrypting messages before broadcast over the commercial paging system. 
     The principles of the present invention may be used independently or in tandem. For example, it is anticipated that the communicator embodiment will be less expensive to implement. Thus, each embodiment may be used to provide OSS support to portions of a SONET network.