MXPA00006961A - System and method for sharing a spare channel among two or more optical ring networks - Google Patents

Abstract

A system and method for sharing a spare channel (316) among two or more optical ring networks (202, 204) that have a common span (316). A first optical cross-connect switch OCCS (308) and a first OCCS controller (306) are placed at one end of the span (316) and a second OCCS switch (312) and a second OCCS controller (310) are placed at the other end of the span (316). The first OCCS (308) and the first OCCS controller (306) are coupled to a first ADM (K, A) from each optical ring, and the second OCCS switch (312) and the second OCCS controller (310) are coupled to a second ADM (G, F) from each optical ring. The first OCCS controller (306) receives alarm indications from each ADM that it is coupled to that senses a ring failure. The second OCCS controller (310) receives alarm indications from each ADM that it is coupled to that senses a ring failure. Upon receiving an alarm indication, the first OCCS controller (306) directs the first OCCS switch (308) to optically couple the ADM that originated the alarm indication to the spare channel (316), and the second OCCS controller (310) directs the second OCCS switch (312) to optically couple the ADM that originated the alarm indication to the spare channel (316).

Description

SYSTEM AND METHOD TO SHARE A REPLACEMENT CHANNEL BETWEEN TWO OR MORE OPTICAL RING NETWORKS The present invention is generally related to optical ring networks. A self-healing optical ring network has three or more ring elements (also called vertices) connected in a logic circuit. Each ring element is connected to two other elements of the ring by means of operating fibers and replacement fibers (also called channels). When wavelength division multiplexing (WDM) is used, one or more fibers can drive an operating channel and a spare channel. An operational channel drives the transit between the elements of the ring during a normal mode of operation. A spare channel also conducts transit between the elements of the ring, but a spare channel can only do so when one of the operating channels in the ring suffers a failure. The elements of the ring may include an add / drop multiplexer (ADM, for its acronym in English). An ADM may pass traffic between the ring 'network and other equipment such as an electrical broadband digital transverse connection (DXC) optical switch and line terminal equipment. In a typical optoelectronic Synchronous Optical Network (SONET) ring network (SONET), an ADM includes a fault detecting unit that detects when a fault has occurred in the channel. For example, an ADM detecting unit will detect a failure in the channel if it detects a loss of serial condition. In response to the detection of a fault, the ADM sends a failure indication (also known as an alarm indication) to a central network management system, and the ADM changes the traffic to a spare channel by means of using the circuit backup to provide a restoration of the ring. Figure 1A illustrates an example of a self-healing optical ring network having four ring elements 102, 104, 106 and 108. In normal mode, operational channels 110, 112, 114, and 116 conduct data around the ring in a single direction and the spare channels 118, 120, 122, and 124 are passive. When a failure occurs in a ring configuration, the spare channels that have not been affected by the fault are activated and direct traffic around the fault in the opposite direction. Figure IB illustrates the operation of a self-healing optical ring network when the operational channel 110, which is designed to drive traffic between the ring element A and the ring element B, suffers a failure. After the ring element A detects a failure in the operational channel 110, the ring element A changes the traffic arriving in the operating channel 116 to a spare channel 124 in the opposite direction to the traffic flow of the operational channel 116. Similarly, after the ring element B detects a failure in the operational channel 110, the ring element B changes the traffic arriving in the spare channel 120 to the operating channel 112 in the opposite direction to the traffic flow of the channel Spare 120. In this way, the ring self-heals when it detects a break in the ring. While the current design of an optoelectronic SONET ring has the advantages of both simplicity and high speed of change, it has the disadvantage of an inefficient reserve to function in proportion to capacity. The reserve for the operating capacity ratio is the number of spare channels in proportion to the number of operating channels. In SONET optoelectronic ring networks the reserve for the operating ratio is 1: 1. That is, for each operating channel, a corresponding spare channel must be available. A self-healing optical network that retains the speed and simplicity of a self-healing SONET ring ed while providing a more efficient use of spare channels is needed.The present invention provides a self-healing optical network that retains the speed and simplicity of a self-healing optical ring network while providing more efficient use of spare channels by means of two or more optical ring networks sharing a spare channel, which in this way reduces the reserve of the operating capacity ratio. In accordance with the present invention, a first optical change unit (OSU) is optically coupled to a first ring element of a first optical ring network, and is optically coupled to a first ring element of an optical ring. a second optical ring network. A second OSU is optically coupled to a second ring element of a first optical ring network, and is optically coupled to a second ring element of a second optical ring network. The first OSU and the second OSU are optically coupled by means of a spare channel that must be shared by a first and a second optical ring network. The first OSU is optically coupled to either the first ring element of the first optical ring network or the first ring element of the second optical ring network to the replacement channel. The second OSU is optically coupled to either the second ring element of the first optical ring network or to the second ring element of the second optical ring network to the replacement channel. In this way the spare channel can be shared between two or more optical ring networks. Additionally, in accordance with the present invention, the first ring element of the first optical ring network and the first ring element of the second optical ring network each send messages to the first OSU. The second ring element of the first optical ring network and the second ring element of the second optical ring network each send messages to the second OSU. In the first embodiment of the present invention, the first ring element and the second ring element of the first optical ring network, upon detecting a fault within the first optical ring network, sends a data message indicating the failure to the first OSU and the second OSU, respectively. Similarly, the first ring element and the second ring element of the second optical ring network, upon detecting a fault within the second optical ring network, sends a data message indicating the failure to the first OSU since the second OSU, respectively. Upon receiving the failure indication from the ring element, the first OSU optically couples that ring element to the spare channel if that ring element is not using the spare channel as a result of a failure event. Similarly, the second OSU, upon receiving the failure indication from the ring element, optically couples that ring element to the spare channel. Accordingly, when a failure occurs in the first optical ring network, the spare channel will be available to the first ring, and when a failure occurs in the second optical ring network, the spare channel will be available to the second ring. In an alternative embodiment of the present invention, the first OSU transmits a status message to each ring element that is optically coupled to the first OSU. The second OSU transmits a status message to each ring element that is optically coupled to the second OSU. A ring element optically coupled to the first OSU will transmit a data message containing a change command to the first OSU if the ring element is not using the spare channel and the ring element detects a fault. Similarly, a ring element optically coupled to the second OSU will transmit a data message containing a shift command to the second OSU if the ring element is not using the spare channel and the ring element detects a fault. Upon receiving the change command, the first and second OSU optically couple the ring element that sent the change command to the spare channel. The additional features and advantages of the present invention, as well as the structure and operation of the different embodiments of the present invention, are described in detail below with reference to the drawings that are attached.

BRIEF DESCRIPTION OF THE DRAWINGS The appended drawings, which are incorporated therein and form part of the specifications, illustrate the present invention and, together with the description, further serve to explain the principles of the invention and to enable a person skilled in the art. relevant to make use of the invention. Figure 1A is a diagram of an optical ring network in a normal mode. Figure IB is a diagram of an optical ring network in a failure mode. Figure 2 is a diagram of two optical ring networks having a common path. Figure 3 is a diagram of a network configuration in accordance with the present invention that allows two optical ring networks to share a spare channel. Figure 4 is a detailed diagram showing the components of the OCCS controller 306. Figure 5 is a detailed diagram of the common path portion of Figure 3 which further shows a network configuration in accordance with the present invention that allows two Optical ring networks share a spare channel. Figures 6A and 6B illustrate two change tables according to an example of the present invention. Figure 7 illustrates a method for sharing a spare channel between the ring networks illustrated in Figure 2 in accordance with one embodiment of the present invention. Figure 8 illustrates a method for sharing a spare channel between the ring networks illustrated in Figure 2 in accordance with a second embodiment of the present invention. . Figure 9 is a diagram of a network configuration in accordance with another embodiment of the present invention that allows two optical ring networks having a common path to share a spare channel. The present invention is described with reference to the appended drawings. In the drawings *, like reference numbers indicate identical or functionally similar elements. Additionally, the digit (s) of the extreme left of a reference number identifies the drawing in which the reference number appears for the first time. The present invention provides a system and method for sharing at least one spare channel between two or more optical ring networks, which in this way provides a more efficient use of spare channels. The present invention is described in the example environment of a fiber optic communications network having two optical rings having a common path. The description of the invention is provided in this environment only for convenience. The invention is not intended to be limited to the application in this environment. In fact, after reading the following description, it will be apparent to the person skilled in the relevant art how to implement the invention in alternative environments. It will be apparent, in particular, how to implement the invention in an environment where any number of optical rings can share any number of spare channels. Figure 2 illustrates two optical ring networks 202 and 204 having a project 201 in common. A path is a path or path between two locations. As shown in Figure 2, the ring network 202 has a ring element 214 in the X position which is connected to a ring element 218 in the Y position by means of an operating channel 206 and a spare channel 208. Similarly, the ring network 204 has a ring element 216 in the X position which is connected to a ring element 220 in the Y position by means of an operating channel 212 and a spare channel 210. As a result of ring network 202 and ring network 204 have a common route between position X and position Y, there are four optical communication channels 206, 208, 210, 212 connecting the position X and Y. Of the four channels optical communication channels 206, 208, 210, 212, two are the spare channels 208, 210. The spare channel 208 serves the ring network 202 and a spare channel 210 serves the ring network 204. The spare channels are passive when a ring network is in the normal mode (ie, no there is ring failure). Consequently, when two or more rings share a common path, there is the passive capacity between a pair of positions. Prior to the present invention, 100 percent of the passive capacity was necessary to support the self-healing restoration independently performed by both ring networks 202, 204. Figure 3 illustrates a network configuration 300 in accordance with the present invention that allows the ring networks 202 and 204 to share a single replacement channel 316 that exists between the X and Y positions. A first optical change unit (OSU) 305 is placed in the X position and a second OSU 307 is placed in the X position. position Y. The OSU 305 includes a first optical cross connect switch (OCCS) 308 coupled to a first OCCS controller 306, and the OSU 307 includes a second OCCS 312 coupled to a second OCCS 310 controller. The OCCS 308 and the OCCS controller 306 may form an integral unit or may exist as two separate units coupled to one another such that the OCCS 306 controller can transmit and receive the OCCS 308 data. or it is true for the OCCS 312 and the OCCS 310 controller.

An OCCS is a device that can change optical paths between a plurality of optical ports. In an example, any of the plurality of optical ports may be coupled internally, optically to any other port within the OCCS. The OCCS controllers 306, 310 control the change of the OCCS 308, 312 respectively. For example, controllers 306, 310 send and receive states and command changes of and for OCCS 308, 312, respectively. More specifically, for example, OCCS 308 and 312 receive commands to be coupled and decoupled from OCCS controllers 306 and 310, respectively. A command to be coupled causes the OCCS to optically couple a first port of the OCCS to a second port of the OCCS. A decoupling command causes an OCCS internally to optically decouple a first port of the OCCS from a second port of the OCCS. Figure 4 further illustrates the OCCS controller 306. The OCCS controller 310 has the same configuration as the OCCS controller 306. The OCCS controller 306 includes a system processor 402, a control logic 404 to be executed by means of the system processor 402 , the memory 406 for storing the coupling state of the OCCS port 308, the exchange table 408 which is stored in the memory 406, the OCCS interface 410 for coupling the OCCS 400 controller to an OCCS, and the network interface of the data 412 for coupling the OCCS 400 controller to a communication network or channel. Figure 5 illustrates the path between positions X and Y in greater detail. As shown in Figure 6, three ports of the OCCS 308 (ports 5, 6, and 7) are optically coupled to three ports of the OCCS 312 (PORTS 5, 6, and 7) by means of an optical link 392. The link Optical communication includes three optical channels: operating channel 314, spare channel 316, and operating channel 318. Specifically, port 5 of OCCS 308 is optically coupled to port 5 of OCCS 312 via operating channel 314; port 6 of OCCS 308 is optically coupled to port 6 of OCCS 312 by means of spare channel 316; and port 7 of OCCS 308 is optically coupled to port 7 of OCCS 312 via operating channel 318. It should be noted that operating channels 314, 318 and spare channel 316 may exist in separate fiber optic cables as shown in Figure 5, or can be multiplexed into a single fiber by means of wavelength division multiplexers (WDMs), as shown in Figure 9. The interface of data network 412 of the OCCS 306 controller is coupled to the port of administration of the network 582 of the element A and the administration port of the network 580 of the element K by means of a communication channel 564. Similarly, the interface of the data network 412 of the OCCS 310 controller is coupled to the port of administration of the network 586 of the element F and to the administration port of the network 584 of the element G by means of the communication channel 568. In one embodiment, all the ring elements are multiplexers of addition / fall ( ADMS). After an ADM detects a ring fault, the ADM transmits a standard ring fault indication to a communication channel connected to its network management port. Consequently, since the OCCS controller 306 is coupled to the network management port of the A element and the K element through the communication channel 564, the OCCS 306 controller will receive the failure indications of the A element and the K element. therefore, the OCCS 306 controller will know if and when a fault has occurred in either the optical ring 202 or the 204. In a similar manner, the OCCS 310 controller will know if and when a fault has occurred either in the optical ring 202 or in the 204. When the ring 202 experiences a channel failure between two elements, the ring 202 will not be able to self-heal unless it has a spare path between the ring elements K and G. Similarly, when the ring 204 experiences a channel failure between two elements, the ring will not be able to self-heal unless it has a spare route between the ring elements A and F. By sharing a single spare channel between the ring networks 202 and 204, unlike the existing optoelectronic SONET rings, the system of the present invention creates a route between the ring elements K and G when a fault occurs in the ring 202 and creates a spare path between the ring elements A and F when a fault occurs in the ring 204. Figure 7 is a flow diagram illustrating the method 700 for creating a spare route between the ring elements K and G when a ring failure occurs. 202 and a method for creating a spare route between the ring elements A and F when a failure occurs in the ring 204, according to one embodiment of the present invention. The method 700 is described below. Method 700 starts at step 701 where control is immediately passed on to step 702. At step 702, the ring element A is optically coupled to port 3 and port 4 of the OCCS 308 by means of the spare channel 554 ' and operating channel 552, respectively. Next, the ring element F is optically coupled to port 3 and port 4 of OCCS 312 by means of spare channel 562 and operating channel 560, respectively (step 704). Next, the ring element G is optically coupled to port 1 and port 2 of OCCS 312 via operating channel 556 and spare channel 558, respectively (step 706). Next, the ring element K is optically coupled to port 1 and port 2 of OCCS 308 via operating channel 548 and spare channel 550, respectively (step 708). After step 708, control proceeds to step 710. In step 710, a change table is created for OCCS controllers 306 and 310. Taking into account the configuration of the network shown in Figure 5, the table The change created by the OCCS controller 306 will be identical to the shift table 600 (see Figure 6A) and the shift table created by the OCCS controller 310 will be identical to the shift table 602 (see Figure 6B). A change table is a table that has at least two columns, a column of events 604 and a column of action 606. That is, that for each event that is detected by an OCCS controller, there is a corresponding course of action that will take the OCCS controller. In one embodiment of the present invention, OCCS controllers 306 and 310 detect three events. The first event is the initiation of the system, the second event is a channel failure in the ring network 202, and the third event is a channel failure in the ring network 204. As described above, the OCCS 306 controller detects a channel fault in the ring network 202 and ring network 204 when the OCCS controller 306 receives a failure indication of the element K and the ring element A, respectively. Similarly, the OCCS controller 310 detects a channel failure in the ring networks 202 and 204 when the OCCS controller 310 receives a failure indication from the ring element G and the ring element F, respectively. When the OCCS controller has detected an event, the OCCS controller will consult with its change table to determine the actions that need to be taken. The OCCS controller will then carry out these actions. After the change tables have been created (step 710), the control goes to step 712. In step 712, the OCCS controllers 306 and 310 wait for an event to occur. If a system initiation event occurs, the control goes to step 720 (step 714). If a channel failure occurs in the ring network 202, the control is passed to step 722 (step 716). If a channel fault occurs in the ring 204, the control is passed to step 732 (step 718). In step 720, the OCCS controllers 306 and 310 will perform the actions corresponding to a system initiation event. That is, the OCCS 306 and 310 controllers will consult with their respective change tables to determine the actions that correspond to an initiation event of the system and then act in accordance with those actions. As shown in Figure 6, rows 608 and 610 of change tables 600 and 602, respectively, contain the actions corresponding to an initiation event of the system. Row 608 of change table 600 instructs the OCCS 306 controller to command OCCS 308 to optically couple port 1 to port 5, port 2 to port 6, port 3 to port 8, and port 4 to port 7 Similarly, row 610 of change table 602 instructs OCCS controller 310 to command OCCS 312 to optically couple port 1 to port 5, port 2 to port 6, port 3 to port 8, and port 4 to port 7. As a result of the above, the internal port couplings of the OCCS, the operational channel 548 is optically coupled with the operational channel 556, which in this way creates an operational path between the ring elements K and G. Similarly, the operating channel 552 is optically coupled with the operating channel 560, which in this way creates an operational path between the ring elements A and F. The replacement channel 550 is optically coupled with the replacement channel 558, which in this way 'creates a path of replacement between the elements K and G. Finally, the replacement channel 554 is optically coupled with the optical passive signal 588, and the replacement channel 562 is optically coupled to an optical passive signal 590. The foregoing can be examined in Figure 5 It should be noted that an arbitrary choice was made to optically couple the replacement channel 550 with the replacement channel 558, which in this way creates a spare route between the ring elements K and G. At the initiation of the system, the The system would have behaved the same if the spare path had been created between the ring elements A and F. It should also be noted that the spare channels 554 and 562 are optically coupled to the passive optical signals 588 and 590, respectively, so that Ring elements A and F do not detect a fault in their respective spare channels. A person who is ordinarily skilled in the relevant art will appreciate that there are no other mechanisms to achieve this goal, and that the invention is not limited to using passive optical signals. After step 720, the ring networks 202 and 204 are fully functional; there is an operative link between each ring element of the ring network 202 and there is an operative link between the ring element of the ring network 204. Consequently, both ring networks can start to transport the traffic data. After step 720, the control is returned to step 712. In step 722 (i.e., when a failure occurs in the ring network 202), the OCCS controller 306 will receive a failure indication from the ring element K on the communication channel 564, and the OCCS.310 controller will receive a failure indication from the ring element G on the communication channel 568. After step 722, the control is passed to step 724 and 728 in parallel. In step 724, the OCCS 306 controller will examine its change table to determine the actions it must take in the event that it receives a failure indication from the ring element K. In this example, the change table 600 instructs the controller OCCS 306 that directs the OCCS 308 to: (1) optically couple port 2 to port 6; and (2) optically coupling port 3 to port 8. After step 724, the control is passed to step 726. In step 726, the OCCS 306 controller will perform those actions by sending the appropriate port coupling commands to the port. OCCS 308. It should be noted that if ports 2 and 3 were coupled to ports 6 and 8, respectively, before the OCCS 306 controller sent the port coupling commands to the OCCS 308, then the OCCS 308 would simply ignore These commands dock the port. But if ports 2 and 3 were not coupled to ports 6 and 8, respectively, before the OCCS 306 controller sent the port coupling commands to the OCCS 308, then, after receiving the port coupling commands, the OCCS 308 would undo ports 2 and 3 of the ports to which they were coupled. In steps 728 and 730, the OCCS controller 310 will perform the same steps as described above with respect to the OCCS controller 306. After the steps 726 and 730 have been carried out, the replacement channel 550 will optically couple at one end of the replacement channel 316 and the replacement channel 558 will optically engage the other end of the replacement channel 316, which in this way creates a spare path between the ring elements K and G. After steps 726 and 730, the control is returned to step 712. In step 732 (i.e., when a failure occurs in the ring network 204), the OCCS controller 306 will receive a failure indication from the ring element A on the communication channel 367, and the OCCS controller 310 will receive an indication of failure of the ring element F. After step 732, the control proceeds to step 734 and 738 in parallel. Steps 734 to 740 are identical to steps 724 to 730. Once steps 736 and 740 are completed, the replacement channel 554 will optically engage one end of the replacement channel 316 and the replacement channel 562 will optically engage at the other end of the spare channel 316, which in this way creates a spare route between the ring elements A and F. After steps 736 and 740, the control is passed to step 712. To summarize, the method that is described above allows the ring network 202 and the ring network 204 to share the spare channel 316. The spare channel 316 is used to create a spare route between the ring elements A and F when the ring network 204 experiences a fault, and the spare channel 316 is used to create a response path between the ring elements G and K when the ring network 202 experiences a failure. In a second embodiment of the present invention, the controllers 306 and 310 do not have change tables. Instead of these, each of the ring elements A, F, G, and K have a table of change. The method 800, which is shown in Figure 8, is a method for sharing the spare channel 316 between the ring networks 202 and 204 in the environment of a second embodiment. The 800 method is described below. Method 800 begins with step 801 where the control immediately goes to step 802. Steps 802 to 808 are identical to steps 702 to 708 and will not be described again in this. After step 808, the control goes to step 810. In step 810, the change table for the ring elements A, F, G, and K has been created. After step 810, the control is passed to the steps 812 and 814 in parallel. In step 812, the OCCS controller 306 will send two status messages on the communication channel 364, a status message for the ring element A and the other status message for the ring element K. The status message for the ring element A informs the ring element A if the spare channel 554 is optically coupled to the spare channel 316 (ie, if internally the OCCS 308 has optically coupled the port with the port 6). In a similar way, the status message for the ring element K informs the ring element K if the spare channel 550 is optically coupled to the spare channel 316 (ie, if internally the OCCS 308 has optically coupled port 2 with the port 6). In step 814, the OCCS controller 310 will send two status messages on the communication channel 587, a status message for the ring element F and the other status message for the ring element G. The status message for the The ring element F informs the ring element F if the spare channel 562 is optically coupled to the spare channel 316. Similarly, the status message for the ring element G informs the ring element G if the channel 558 is optically coupled to the spare channel 316. After step 812 and step 814 the control goes to step 815. In step 815 the OCCS controllers 306 and 310 wait until a ring fault occurs. If the failure occurs in a ring network 202, the control is passed to step 818, otherwise, the control is passed to step 828. In step 818 the ring elements K and G will detect the f_Ala in the ring network 202. In response to the detection of the fault, the elements K and G will use the status message they have already received from the OCCS controller 306 and the OCCS controller 310, respectively, to determine if they are optically coupled to the spare link 316 (step 820). If the elements K and G are already optically coupled to the spare link 316, then the elements K and G will use the replacement channels 550 and 558, respectively (step 822). However, if the element K is not optically coupled to the spare link 316, then the element K will consult its change table and, based on the contents of the table, sends a change command to the OCCS 306 controller over the channel 554. The change command will direct the OCCS controller 306 to issue a command to the OCCS 308 so that the element K is optically coupled to the spare channel 316 (step 824). Similarly, if the G element is not optically coupled to the spare link 316, the G element will consult its change table and, based on the contents of the table, send a change command to the OCCS 310 controller over the channel 568. The change command will direct the OCCS controller 310 to issue a command to the OCCS 312 so that the element G is optically coupled to the spare channel 316 (step 826). Elements A and F follow the same procedure as elements K and G in the event of a ring failure in ring 2Q4 (steps 828 to 936). After steps 826 and 836 the control is returned to step 812. By using the above procedure, a spare route operating between the ring elements K and G will be created when a fault occurs in ring 202, and will create a spare path that will operate between ring elements A and F when a fault occurs in ring 204. In this way, rings 202 and 204 share spare channel 316. Figure 9 illustrates another alternative embodiment of the present invention. As shown in Figure 9, the optical link 392, which is used to optically couple the OCCS 308 and OCCS 312, includes a wavelength division multiplexer (WDM) 908 and WDM 912 connected between the OCCS 308 and OCCS 312 The WDM 908 and the WDM 912 are optically coupled by means of the fiber 910. The WDM 908 is optically coupled to the ports 5, 6, and 7 of the OCCS 308 by means of the operating channel 902, the spare channel 904, and operating channel 906, respectively. Similarly, WDM 912 is optically coupled to ports 5, 6, and 7 of OCCS 312 via operating channel 914, spare channel 916, and operating channel 918, respectively. The previous alternative mode (which adds WDMs) works exactly the same as the preferred mode. In other words, change tables 600 and 6O2 and methods 700 and 800, as described above, also apply to this WDM embodiment of the present invention as will be apparent to a person skilled in the relevant art. While various embodiments of the present invention have been described above, it should be understood that these have been presented as examples, and not as limitations. It will be understood by those skilled in the art that many changes can be made in form and detail therein without departing from the spirit and scope of the invention as defined by the following claims. Therefore the width and scope of the present invention should not be limited by any of the exemplary embodiments described above, but should be defined only in accordance with the following claims and their equivalents.

Claims (26)

1. An optical communications system having a first optical ring network and a second optical ring network, wherein the first optical ring network has a first ring element and a second ring element, and wherein the second ring network The optical device has a first ring element and a second ring element, comprising: a first optical change unit, optically coupled to the first ring element of the first optical ring network and to the first ring element of the second ring network optical; a second optical change unit, optically coupled to the second ring element of the first optical ring network and to the second ring element of the second optical ring network; and a spare channel optically coupled between the above first optical shift unit and the previous second optical shift unit, wherein the first optical shift first selectively and optically engages one of the first ring element of the first optical ring and the first element of the second optical ring to the previous replacement channel, and the second second optical change unit selectively and optically couples one of the second ring element of the first optical ring and the second element of the second optical ring to the previous replacement channel . The system according to claim 1, wherein the first first optical change unit comprises a first optical transverse connection switch coupled to a first controller, and the previous second optical change unit comprising a second optical connection switch transverse coupled to a second controller. The system according to claim 2, wherein the first first controller includes the receiving elements for receiving indications of failure of the first ring element of the first optical ring and of the first ring element of the second optical ring. The system according to claim 3, wherein the previous controller includes the second receiving elements for receiving indications of failure of the second ring element of the first optical ring and of the second ring element of the second optical ring. The system according to claim 4, wherein the first ring element of the first optical ring transmits a first fault indication to the first first controller on the first ring element of the first optical ring that detects a ring fault in the first ring. first optical ring. The system according to claim 5, wherein the second ring element of the first optical ring transmits a second fault indication to the previous second controller on the second ring element of the first optical ring that detects a ring fault in the first ring. first optical ring. 7. The system in accordance with the claim 6, wherein the former first controller includes a first change table, the previous change table having an event column and an action column. 8. The system in accordance with the claim 7, wherein the previous first controller consults the previous first change table upon receiving the previous indication of failure of the previous first ring. The system according to claim 8, wherein the former first controller sends a command corresponding to an action on the first first change table to the first first transverse connection optical switch after consulting the previous first change table . The system according to claim 9, wherein the above second optical change unit includes a second shift table, the previous second shift table having an event column and an action column. The system according to claim 10, wherein the previous second controller .consults the previous second shift table upon receiving the previous second failure indication. 1

2. The system according to claim 11, wherein the previous second controller sends a command corresponding to an action on the previous second shift table to the previous second transverse connection optical switch after consulting the previous second shift table. The system according to claim 1, wherein the first element of the first optical ring is an add / drop multiplexer. The system according to claim 1, wherein the first first optical change unit sends the status information to the first ring element of the first optical ring. 15. The system in accordance with the claim 14, wherein the first ring element of the first optical ring transmits a change command to the first optical change unit when the first ring element of the first optical ring detects a ring fault and when the previous state information indicates that the The above replacement channel is not optically coupled to the first ring element of the optical ring. 16. The system according to claim 1, wherein the first first optical change unit is connected to the previous second unit of. optical change by means of an optical link. The system according to claim 16, wherein the above optical link includes a spare fiber optic cable, the above replacement fiber optic cable which is connected to a first port of the above first optical change unit with a first port of the above second optical change unit, wherein the above replacement fiber optic cable conducts said spare channel. 18. The system in accordance with the claim 16, wherein the above optical link includes a first and a second wavelength division multiplexer (WDMs), wherein, the former first WDM is connected to the previous second WDM by means of a fiber optic cable, the previous cable fiber optic that drives the previous spare channel. 19. A method for sharing a spare channel between a first and a second optical ring, wherein the first optical ring has a first ring element and a second ring element, the second optical ring has a first ring element and a second ring element that are optically coupled to a first transverse connection optical switch, the second ring element of the first optical ring and the second ring element of the second optical ring that are optically coupled to a second optical switch of transverse connection, and the replacement channel optically coupled to the first and second transverse connection optical switch, which method comprises the steps of: (a) receiving a first indication of failure of the first ring element of the first optical ring and the first ring element of the second optical ring; (b) optically coupling the first ring element of the first optical ring with the spare channel if the first ring element of the first optical ring transmitted the first fault indication; and (c) optically coupling the first ring element of the second optical ring with the spare channel if the first ring element of the second optical ring transmitted the first indication of failure. 20. The method of compliance with the claim 19, further comprising the steps of: (d) receiving a second indication of failure of one of the second ring elements of the second optical ring; (e) optically coupling the second ring element of the first optical ring with the spare channel if the second ring element of the first optical ring transmitted the second fault indication; and '(f) optically coupling the second ring element of the second optical ring with the spare channel if the second ring element of the second optical ring transmitted the second fault indication. 21. The method according to the claim 20, wherein step (b) includes the steps of consulting a first shift table and sending a command? E change corresponding to an action on the first first shift table to the first transverse connection optical switch. 22. The method of compliance with the claim 21, wherein step (e) includes the steps of consulting a second shift table and sending a shift command corresponding to an action on the previous second shift table to the second transverse connection optical switch. 2

3. A method for sharing a spare channel between a first and a second optical ring network, wherein the first optical ring network has a first ring element and a second ring element, the second optical ring network has a first ring element and a second ring element, the first ring element of the first optical ring and the first ring element of the second optical ring which are optically coupled to a first change unit, the second ring element of the first optical ring and the second ring element of the second optical ring which are optically coupled to a second change unit, and the replacement channel optically coupled to the first and second optical shift unit, which method comprising the steps of: (a) sending a first status message of the first optical change unit to the first ring element of the second optical ring; (b) detecting a ring fault in the first optical ring; (c) using the above first status message, which determines whether- the first ring element of the first optical ring is optically coupled to the spare channel; (d) if the first ring element of the first optical ring is not optically coupled to the spare channel, send a first change command of the first ring element of the first optical ring to the first optical change unit; and (e) upon receiving the first change command in the first optical change unit, optically coupling the first ring element of the first optical ring to the previous replacement channel through the first optical change unit. The method according to claim 23, further comprising the step of (f) sending a second status message of the second unit "optical change to the second ring element of the first optical ring to the second ring element of the second optical ring 25. An apparatus for sharing a spare channel between a first and a second optical ring network, wherein the first optical ring network has a first ring element and a second ring element, and the second network of The optical ring has a first ring element and a second ring element comprising: a first receiving element a first indication of failure of one of the first ring elements of the first optical ring and the first ring element of the second optical ring; a first element for coupling that is responsive to the first first receiving element for optically coupling the first ring element of the first optical ring with the reflectance channel This is when the first ring element of the first optical ring transmits the first fault indication to the first first receiving element, and to optically couple the first ring element of the second optical ring with the replacement channel when the first ring element of the second ring optical transmits the first indication of failure to the previous first receiving element. 26. The system according to claim 25, further comprising: a second receiver element a second fault indication of one of the second ring elements of the first optical ring and the second ring element of the second optical ring; and a second element for coupling that is responsive to the previous second receiving element for optically coupling the second ring element of the first optical ring with the spare channel when the second ring element of the first optical ring transmits the second indication of failure to the previous one. second receiving element, and for optically coupling the second ring element of the second optical ring with the spare channel when the second ring element of the second optical ring transmits the first indication of failure to the previous second receiving element.