MXPA96005246A - Architecture sonet de multiples anil - Google Patents

Abstract

The present invention relates to a pair of SONET rings (12 'and 14') that can be interconnected by providing at least two gates (16_m-1 and 16_m) that are shared by each of the rings. Each shared gate has the ability to transfer a block of optical information resident in a prescribed time slot in an exchange box associated with a ring to a time slot in an exchange box associated with the other ring, such that the block reaches its intended destination in that anil

Description

SONET ARCHITECTURE OF MULTIPLE RINGS Technical Field This invention relates to synchronous optical network architecture (SONET = Synchronous Optical NETwor), which is characterized by a plurality of interlaced fiber rings. An e s Currently, synchronous optical network rings (SONET) are used to transport telecommunications traffic between cities. A typical SONET ring comprises a plurality of cubes or nodes, each coupled to another by means of at least one fiber optic link. At each node, a gate converts an electrical input signal that may be associated with a telephone call to an optical information block. The gate places the optical information block on the ring within a particular time slot of an exchange frame having a particular synchronization (speed). Each time slot in each frame corresponds to a particular destination (ie node) within the ring. In this way, the gate on each node converts the information block that appears within the time slot associated with that node into corresponding electrical signals. In this way, traffic is automatically routed on the ring.

REP: 23401 Connecting a large number of nodes (ie gates) in a single ring is often impractical. On the contrary, some nodes can be organized in smaller (subsidiary) rings that are connected to each other by a main structure ring to minimize the length of the fiber links. Each subsidiary ring is typically intertwined (and interconnected) to the main structure ring in a pair of nodes. In the past, this interconnection is achieved by providing means at each interconnected node of the subsidiary ring to convert an optical information block into corresponding electrical signals. These electrical signals are transmitted to a corresponding interconnected node of the main structure ring for conversion to an optical information block for transmission on the main structure ring within a particular time slot associated with the destination of that information block. The information is passed from the main structure ring to a subsidiary ring in the same way as described above. In practice the subsidiary and main structure rings must be controlled separately, making the provision problematic. In this way, to provide a customer with end-to-end conductivity, it may be necessary to provide a large number of rings. Furthermore, the equipment required in the interconnected cubes to convert each block of optical information into corresponding electrical signals and to convert the electrical signals into a corresponding block of optical information is costly and increases the overall complexity of the transmission network, decreasing from this way its reliability. In this way, there is a need for a SONET ring architecture that overcomes the previous disadvantages. SUMMARY OF THE INVENTION Briefly, the present invention relates to an optical fiber transmission system comprising at least one main ring and one subsidiary ring. Each main ring comprises m (where m is an integer greater than two) nodes linked together in chain form fragmented by m first links of optical fibers. In each of the first J? -2 nodes there is a first gate in which electrical input signals are converted into at least one optical information block synchronized with a first exchange frame, such that the block resides in a particular time slot in the box associated with its final destination. Each first gate also converts each block of information that arrives at that gate into an associated time slot in corresponding electrical signals. Each subsidiary ring comprises n (where n is an integer greater than two) second nodes that are coupled together in the form of a fragmented chain by n second links of optical fibers. In each one of n-2 seconds nodes of each subsidiary ring there is a second gate in which electrical signals are converted at least in one block of optical information synchronized with a second exchange table, such that each block resides in a particular time slot in that frame associated with its final destination. Each second gate also converts each block of information that this gate reaches into the time slot in the second associated exchange in corresponding electrical signals. In accordance with the invention, each of the two nodes and each of the nodes that lack individual gates share a third gate. Every third gate shared by one of the myn nodes converts electrical input signals into at least one block of optical information synchronized to an exchange frame such that the block resides in a particular time slot associated with its destination within one of the subsidiary main rings. Each third gate serves to convert a block of information that arrives at that gate within an associated time slot into corresponding electrical signals. In addition, at least one third gate shared by one of the myn nodes transfers a block of information that is destined from one gate apparatus to another ring, by transferring the block from its current time slot in its current exchange box to a slot of time in an exchange table associated with the destination of the block. In this way, the third gateway transfers a block of information from the main ring to a subsidiary ring and vice versa. According to another aspect of the invention, the first, second and third gates are all controlled by a single master controller capable of programming each gate. In particular, the master controller regulates which time slot in a corresponding exchange frame is associated with a particular gate, thereby altering the addressing of blocks of information in each ring. By controlling the gates in this manner, the controller can jointly provision and administer and maintain both the main and subsidiary rings. Brief description of s pjbujps FIGURE 1 is a block diagram of an optical fiber transmission according to the prior art; FIGURE 2 is a block diagram of an exchange chart according to the prior art; FIGURE 3 is a schematic block diagram of an optical fiber transmission system according to the invention; and FIGURE 4 is a schematic block diagram of a pair of exchange slots illustrating how the transmission system of FIGURE 3 transfers a block of information between slots. Detailed Description FIGURE 1 illustrates a fiber optic transmission network of the prior art 10, comprising part of a larger telecommunications network. The network 10 comprises a plurality of SONET rings, with two of these rings 12 and 14 which are illustrated in the Figure. Ring 12 comprises mdi-16 nodes, (where m is an integer greater than two) each node linked to another in a chain shape fragmented by a set of optical fiber links 18-18. Ring 14 is constructed in a manner similar to ring 12 and comprises n nodes 20Í-20;, (where n is an integer) each node linked to another node in a chain shape fragmented by a set of optical fiber links 22-22 . In practice, each gate in each of the rings 12 and 14 can be linked to an adjacent gate in the same ring, at least by two fiber optic links, only one of which is illustrated in Figure 1. A link typically it is used to carry normal or service traffic, while the other link remains in reserve to use during service interruptions. Each of the nodes 16X-165 comprises a gate, typically in the form of a fiber terminal, capable of converting electrical signals, such as those carrying telecommunications traffic, into at least one optical information block. Each optical information block generated by each of the gates ldi-16 »is synchronized to a separate exchange table 24 (illustrated in Figure 2) associated with the ring 12. With reference to Figure 2, each exchange table 24 it comprises a time interval of a predetermined duration (typically 125 micro seconds) which is divided into a plurality of time slots i- .. Each optical information block generated by each of the gates ld? -16 »occupies a particular the time slots T, according to the intended destination node for that information block within the ring. The gateway in the intended destination node converts the information block into the corresponding time slot associated with that node in a set of electrical signals. With reference to Figure 2, a block of information Bi is placed in the time slot Tx of the exchange box 24 when the block is destined for the gate associated with that time slot. In a similar manner, the information block Bx intended for another destination gate will occupy the time slot T2 associated with that destination gate. In practice the ring 12 may comprise an OC-48 ring whose exchange frame each has 48 separate slots.

With reference to Figure 1, the gates lßi-lß * typically each comprise a fiber terminal AT & Model FT 2000 that operates to generate the optical information blocks for steps on the ring 12 and to convert each block arriving in the gate in a set of corresponding electrical signals. In practice, the gate 16x can be supplied with telecommunications traffic by a multiplexer 26 through an optical fiber link 27. Together, the multiplexer 26 and the gate 16 ,. they can serve as a point of presence 28 of a carrier between exchanges such as AT & T, within a local exchange (LEC). Each of the remaining 162-16- gates is typically located within an urban center (LSO) 30 of the LEC. In this way, the telecommunications traffic can pass between any of the LSOs 30-30 and IXC POP 28 through the ring 12. A master controller 32, typically a digital computer or the like, controls each of the gates lß ^ lß » by programming each gate to respond to a particular time slot within the interchange frame 24 of FIG. 2. By programming each of the gates I61-I6 »in this manner, the master controller 32 can effectively provide as well as manage and control ring 12, by regulating the destination of the information blocks within the ring.

The ring 14 typically operates in a manner very similar to the ring 12. Each of the gates 20, -20, comprises a device such as a digital multiplexer that converts electrical signals into at least one optical information block that is synchronized to a exchange box (not shown) which may have the same or different synchronization as table 24. Each block of information generated by each of the gates 20? -20_jj occupies a specific slot in the exchange table according to the intended destination of the exchange. block inside the ring 14. Typically the 20L gate is located in the customer premises, while the 202-20s gates are each located in one of a set of LSOs 30-30. In practice the ring 14 may be an OC-3 ring having only three slots (i.e., n = 3) within each exchange frame. In this way, the ring 14 typically has a synchronization that is different (ie slower than the ring 12). Like the ring 12, the ring 14 includes a master controller 34 which controls the gates 20, -20 ^ when programming each gate with respect to the time slot in which it responds. In this way, the master controller 34 provisions, as well as manages and maintains the ring 14 in a manner very similar to the master controller 32 that provisioned the ring 12.

In many cases, it may be convenient to pass a block of information that runs in one of the rings 12 and 14 to the other ring. For that purpose, a pair of gates 16, -16 »are interconnected (interleaved) to a pair of gates 20, -20". In the embodiment illustrated in Figure 1, nodes 163 and 16 are interconnected with nodes 20, and 20n, respectively. According to the prior art, each of the nodes 163 and 16"is interconnected to a corresponding one of the nodes 20, and 20n by a separate one of a pair of digital cross-connect devices 36-36, typically DACS IV cross-connect systems. -2000 manufactured by AT & T. Each cross-connect device 36 carries electrical signals supplied from one of the pair of interconnected gates 163 and 164 to a corresponding one of the interconnected gates 20, and 20"respectively and vice versa. In order to direct an optical information block of the ring 12 to the ring 14, one of the gates 163 or 164 will convert the intended block into electrical signals. The signals are then supplied to the corresponding of the gates 20, and 20"through an associated digital cross-connect device 36-36. The electrical signals received in the corresponding of the gates 20, and 20, then converted back to an optical information block to transmit on the ring 14. Each optical information block destined to pass from the ring 14 to the ring 12, likewise becomes electrical signals in one of the gates 20 , and 20"for passage through one of the cross connection devices 36-36 to a corresponding one of the gates 163 and 164. The interconnection of the rings 12 and 14 in this way contributes to the total cost and complexity of the network 10 due to the need to provide the digital cross connection system 36 for transporting electrical signal between the interconnected nodes. Still further, the dual ring interconnect architecture described above with respect to Figure 1 has the disadvantage that rings 12 and 14 as well as digital cross-connect devices 36-36 are provisioned separately, making connectivity more difficult to achieve. from end to end. Now with reference to Figure 3, a telecommunication network of optical fiber transmission 10 'according to the invention is illustrated. Like network 10 of Figure 1, network 10 'of Figure 3 comprises at least two SONET rings 12' and 14 '. The ring 12 'comprises a plurality of m nodes where m is an integer greater than two. Unlike the ring 12 of Figure 1, where each node has its own gate, there are at most m least 2 nodes within the ring 12 'of Figure 3, which have their own gates Iß ^ -lß' »^ respectively . Each node having one of the discrete gates ie ', - 16', - 2 is linked to another discrete gate via an optical fiber link 18 '. The gate 16 ', of the ring 12' of Figure 3 is typically coupled to a multiplexer 26 'via an optical fiber link 27', which together serves as a POP 28 'for an IXC in a manner very similar to the gate 16a and multiplexer 26 of Figure 1 comprise the POP 28. The remaining gates 16'2-16'5_2 are typically located in the LSOs 30-30 as the gates 162-16"reside in the LSOs 30-30 in Figure 1. As the ring 14 of Figure 1, the ring 14 'of the Figure 3 comprises n nodes (where n is an integer greater than 2) of which no more than n-2 nodes each have a gate 20. In the embodiment shown in Figure 3, n = 3 such that the ring 14 'only contains a simple discrete gate 20', in a corresponding one of the 3 nodes. Typically, the gate 20 'serves as a customer gate, in a manner very similar to the gate 20', of the ring 14 of FIG. 1. In accordance with the invention, at least two of the nodes of the ring 12 'of Figure 3, each shares one of a pair of common gates 16 '"_, and 16'" respectively with a pair of nodes of the ring 14 '. The common gates 16'B., And 16 '"each are linked by an optical fiber link of 18 xa to a separate one of the discrete gates 16', - 16 ', .- 2 to form a fragmented chain assembly comprising the ring 12 '. In a similar manner, each of the common gates 16'5_, and 16 '"is also linked by an optical fiber link 22' to the gate 20 ', to form a fragmented chain assembly comprising the ring 14'. The common gates 16 '-,., And 16' "typically each reside in a separate one of the LSOs 30'-30 '. In practice each of the common gates 16 '-,., And 16' "comprise a fiber terminal model FT 2000 is controlled (ie program) from a master control 32 'together with each of the gates 16'1 -16 '"_ 2 and gate 20' ,. The master controller 32 'typically comprises a digital computer or the like that is capable of programming each of the gates and the gate 20', to respond to a particular time slot within each exchange frame associated with each ring, in a form similar to the way in which controllers 32 and 24 of Figure 1 separately control ring 12 and ring 14 of Figure 1. In addition, master controller 32 'also programs each of the common gates 16',., and 16 '"(shared) 16'" _, and 16 to respond to a "destination" time slot and an "interoperation" time slot in each exchange frame associated with each ring. To understand the manner in which the master controller programs the common gates 16, and 16 'ß, reference * should be made to Figure 4 which illustrates exchange frames 24' and 40 associated with the rings 12 'and 14' in the Figure 3. Information blocks on the ring 12 'of Figure 3 are transmitted in a plurality of synchronized exchange frames 24' (only one is illustrated in Figure 4), each frame comprises a plurality of time slots T, -TB , each one occupied by a separate block. Likewise, information blocks are transmitted on the ring 12 'of Figure 3 in a plurality of synchronized exchange frames 24' (only one is illustrated in Figure 4), each frame comprises a plurality of time slots T, -TB , each one occupied by a separate block. For discussion purposes it was considered that the common gate 16 '"is programmed by the controller 32' of Figure 3 to respond to time slots T3-Ta in the exchange frames 24 'and 40', respectively as time slots of destination. For each block of information appearing in a separate from these slots of these target slots, the common gate 16 '»converts the block into electrical signals for further processing in the corresponding LSO 30'. In this way, an information block passes over each of the rings from a source node to its destination node in the same ring.

Now considering that the common gate 16 '"has been programmed by the controller 32' to respond to the time slots T, -T", as interoperation slots within the exchange frames 24 'and 40' respectively of the Figure. Upon receiving a block of information in the interoperation slot T, in the exchange frame 24 'of Figure 4, the common gate 16' »of Figure 3 transfers the optical information block to a corresponding time slot within the frame 40 'exchange associated with the final destination of that block in ring 14' in Figure 3. In a similar way, the common gate 16 '"responds to each block of information appearing in the time slot T" within the exchange frame 40' associated with the ring 14 'of Figure 3. Each block of information appearing in the slot of time T "is transferred through the common gate 16 '» to a corresponding time slot in the exchange box 24' for transit on the ring 12 'of Figure 3 to its final destination. In comparison with the prior art network 10 of Figure 1, the network 10 'according to the invention produces several distinct advantages. First, all gates 16 ', - 16' "and gate 20 'are regulated by the same master controller 32'. In this way both of the rings 12 'to 14' can be supplied or provisioned as well as managed and maintained by the controller 32 'at the same time. In addition, the network 10 'has the advantage of providing node 20,', (of the client facilities) with a fully redundant dual-port assembly (which is provided by the optical links linking the client facilities with the common gates). 16 '»., And 16'»). Additionally, the network 10 'of Figure 3 characterizes the capacity for transporting information between the rings, with a minimum of physical equipment, thus reducing capital expenditures. The network 10 'of Figure 3 has been found to produce another distinct advantage in terms of restoration time, ie the amount dedicated to restoring the network in the event of a service failure. Typically, the network 10 can be restored within approximately 35 milliseconds, while the restoration time for the network 10 is typically in the order of 110 milliseconds. It will be understood that the embodiments described above are merely illustrative of the principles of the invention. Various modifications and changes can be made by those skilled in the art that will incorporate the principles of the invention and fall within the spirit and scope thereof. It is noted that in relation to this date, the best method known to the applicant to carry out the aforementioned invention, is that which is clear from the present description of the invention.

Having described the invention as above, property is claimed as contained in the following:

Claims (9)

1. CLAIMS 1.- A fiber optic transmission system, comprising: at least one main ring that has m first nodes, no more than m-2 of which each contains a first gate linked to another first gate associated with another gate. the m-2 nodes by a first fiber optic link in a fragmented chain configuration, each first gate converts electrical input signals into an optical information block synchronized with an exchange frame associated with the main ring, such that the block resides in a time slot within the exchange frame associated with a destination within the main ring and each first gate responds to a particular time slot within the exchange box to convert a block of information resident in the particular slot into electrical signals of exit; at least one subsidiary ring having n first nodes, no more than n-2 of which each contains a second gate, each second gate converts electrical input signals into an optical information block synchronized to an exchange frame associated with the subsidiary ring, such that the block resides in a time slot within the exchange box associated with a destination within the subsidiary ring, and each second gate responds to a particular time slot within the exchange box to convert a block of information resident in the particular slot in electrical output signals, wherein the improvement is characterized in that it comprises; at least two third gates each shared by one of the nodes m and n lacking first and second gates respectively; each third gate is linked by second fiber optic links to a pair of first gates in the form of a fragmented chain to complete the main ring and the third gates connected by third links of optical fibers with at least one second gate in the form of a fragmented chain for completing the subsidiary ring, every third gate converts a block of information destined for that gate into corresponding electrical signals and at least one third gate that transfers one block of information to another gate on another ring when transferring the block from its current time slot into its current exchange frame to a time slot in an exchange table associated with the destination of the block; and a master controller to control the first, second and third gates.
2. Apparatus according to claim 1, characterized in that the master controller comprises a digital computer for programming the first and second gates to respond to first and second time slots within the first and second exchange frames, respectively, to program each third gate to respond to a destination time slot and an interconnect time slot within each of the first and second exchange frames.
3. Apparatus according to claim 1, characterized in that each third gate is resident within a local exchange (LSO) of a telecommunications network.
4. 4. Apparatus according to claim 1, characterized in that at least one second gate is located in a customer premises and where the second gate in the customer premises is connected to at least two and three gates to provide dual landfall. complete redundant for the second gate.
5. 5. A method for interconnecting first and second SONET rings, each ring has an associated exchange frame comprising a plurality of time slots for occupying optical information blocks according to the destination of the blocks: verifying each exchange table of each ring in a gate shared by first and second rings, to determine if the block of information is present in a prescribed time slot in a swap box designed to hold an information block for transfer between rings, and if said block is present in one of the prescribed slots, then transfer the block from one ring to another ring, such that the block resides in a time slot associated with its destination within the ring; while the floodgates are controlled jointly.
6. 6. Method according to claim 5, characterized in that the exchange frames associated with first and second rings have different synchronizations.
7. 7. Method according to claim 6, characterized in that the second ring SONET has a synchronization smaller than the first ring.
8. 8. Method according to claim 5, characterized in that each block of optical information is transferred optically between rings.
9. 9. Method according to claim 5, characterized in that the gates are provisioned, managed and maintained together.