METHOD AND SYSTEM FOR ALLOCATING DEDICATED PROTECTED SPECTRUM BASED ON CROSSTALK AWARENESS

Abstract

The present invention relates to a method and system for allocating a dedicated protected spectrum based on crosstalk awareness, including calculation, core selection, a modulation format, and spectrum allocation. First, working paths are first established: selecting a modulation format; determining a maximum allowable crosstalk value, classifying cores, calculating inter-core crosstalk values of all available spectrum blocks, and selecting a spectrum block with the smallest crosstalk value for allocation; and then dedicated protection paths are established: selecting a modulation format; determining a maximum allowable crosstalk value, classifying cores, calculating inter-core crosstalk values of all available spectrum blocks, and selecting a spectrum block with the smallest crosstalk value for allocation. The present invention improves the spectrum resource efficiency of a space-division multiplexing elastic optical network, reduces a crosstalk value of each fiber link, and implements the survivability of a space-division multiplexing optical network.

Claims

1. A method for allocating a dedicated protected spectrum based on crosstalk awareness, comprising steps of: step S1: initializing a space-division multiplexing elastic optical network, and generating a connection request; step S2: calculating a plurality of working paths from a source node to a destination node, and determining whether the working paths are successfully established, wherein if not, the connection request is blocked, or if yes, the shortest path of the plurality of working paths is selected, a corresponding modulation format is selected according to the shortest path, and a quantity of spectrum slots required for the connection request and a first maximum allowable crosstalk threshold on a fiber optic link are determined according to a bandwidth demand of the connection request and the selected modulation format; step S3: classifying cores according to the quantity of required spectrum slots, setting priorities for the cores, and determining whether available spectrum blocks in the cores meet a spectrum consistency constraint and a spectrum continuity constraint, wherein if not, the connection request is blocked, or if yes, inter-core crosstalk values of all available spectrum blocks are calculated, and it is determined whether the first maximum allowable crosstalk threshold is exceeded, and if yes, the connection request is blocked, or if not, a spectrum block with the smallest crosstalk value is selected for spectrum allocation; step S4: deleting the currently established working paths, calculating a plurality of dedicated protection paths from a source node to a destination node, determining whether the dedicated protection paths are successfully established, wherein if not, the connection request is blocked, or if yes, the shortest path of the plurality of dedicated protection paths is selected, a corresponding modulation format is selected according to the shortest path, and a quantity of spectrum slots required for the connection request and a second maximum allowable crosstalk threshold on a fiber optic link are determined according to a bandwidth demand of the connection request and the selected modulation format; and step S5: classifying cores according to the quantity of required spectrum slots, setting priorities for the cores, and determining whether available spectrum blocks meet a spectrum consistency constraint and a spectrum continuity constraint, wherein if not, the connection request is blocked, or if yes, inter-core crosstalk values of all available spectrum blocks are calculated, and it is determined whether the second maximum allowable crosstalk threshold is exceeded, and if yes, the connection request is blocked, or if not, a spectrum block with the smallest crosstalk value is selected for spectrum allocation.

2. The method for allocating a dedicated protected spectrum based on crosstalk awareness according to claim 1, wherein during the calculation of the plurality of working paths from the source node to the destination node, the working paths of the connection request are calculated by using a multiple shortest path algorithm.

3. The method for allocating a dedicated protected spectrum based on crosstalk awareness according to claim 1, wherein during the calculation of the plurality of dedicated protection paths from the source node to the destination node, the dedicated protection paths of the connection request are calculated by using a multiple shortest path algorithm.

4. The method for allocating a dedicated protected spectrum based on crosstalk awareness according to claim 1, wherein during the classification of the cores according to the quantity of required spectrum slots and the setting of the priorities for the cores, a core with the highest priority is selected according to the quantity of required spectrum slots for transmission, if a corresponding core fails to be found, a core with a relatively high priority in cores of other types is selected for transmission, if a core still fails to be found, transmission is performed in a public core, and if transmission fails to be performed in a public core, it is determined that the connection request is blocked.

5. The method for allocating a dedicated protected spectrum based on crosstalk awareness according to claim 1 or 1, wherein it is determined whether the available spectrum blocks meet the spectrum consistency constraint and the spectrum continuity constraint, if the available spectrum blocks do not meet the spectrum consistency constraint and the spectrum continuity constraint, a core with a next priority is selected, and if none of the cores has an available spectrum block, the connection request is blocked.

6. The method for allocating a dedicated protected spectrum based on crosstalk awareness according to claim 1, wherein a method for calculating the inter-core crosstalk values of all the available spectrum blocks comprises: calculating an impact value between each spectrum block and a spectrum block of an adjacent core; then calculating crosstalk values with all adjacent cores, wherein if crosstalk values on all links are less than the first maximum allowable crosstalk threshold or the second maximum allowable crosstalk threshold, spectrum resource allocation schemes are kept, or otherwise, the connection request is blocked; and finally, selecting a scheme with the smallest crosstalk value from all the spectrum resource allocation schemes, and then allocating spectrum resources.

7. The method for allocating a dedicated protected spectrum based on crosstalk awareness according to claim 1, wherein the first maximum allowable crosstalk threshold is the same as the second maximum allowable crosstalk threshold.

8. The method for allocating a dedicated protected spectrum based on crosstalk awareness according to claim 1, wherein after step S5 is completed, a performance parameter of the network is evaluated according to a quantity of spectrum resources used in the entire network.

9. The method for allocating a dedicated protected spectrum based on crosstalk awareness according to claim 8, wherein after the performance parameter of the network is evaluated, a network status is monitored; and judgment and early warning are performed on the network.

10. A system for allocating a dedicated protected spectrum based on crosstalk awareness, comprising: a connection request module, configured to: initialize a space-division multiplexing elastic optical network, and generate a connection request; a working path establishment module, configured to: calculate a plurality of working paths from a source node to a destination node, and determine whether the working paths are successfully established, wherein if not, the connection request is blocked, or if yes, the shortest path of the plurality of working paths is selected, a corresponding modulation format is selected according to the shortest path, and a quantity of spectrum slots required for the connection request and a first maximum allowable crosstalk threshold on a fiber optic link are determined according to a bandwidth demand of the connection request and the selected modulation format; a core classification module, configured to: classify cores according to the quantity of required spectrum slots, set priorities for the cores, determine whether available spectrum blocks in the cores meet a spectrum consistency constraint and a spectrum continuity constraint, wherein if not, the connection request is blocked, or if yes, inter-core crosstalk values of all available spectrum blocks are calculated, and it is determined whether the first maximum allowable crosstalk threshold is exceeded, and if yes, the connection request is blocked, or if not, a spectrum block with the smallest crosstalk value is selected for spectrum allocation; a dedicated protection path establishment module, configured to: delete the currently established working paths, calculate a plurality of dedicated protection paths from a source node to a destination node, determine whether the dedicated protection paths are successfully established, wherein if not, the connection request is blocked, or if yes, the shortest path of the plurality of dedicated protection paths is selected, a corresponding modulation format is selected according to the shortest path, and a quantity of spectrum slots required for the connection request and a second maximum allowable crosstalk threshold on a fiber optic link are determined according to a bandwidth demand of the connection request and the selected modulation format; and a spectrum allocation module, configured to: classify cores according to the quantity of required spectrum slots, set priorities for the cores, and determine whether available spectrum blocks meet a spectrum consistency constraint and a spectrum continuity constraint, wherein if not, the connection request is blocked, or if yes, inter-core crosstalk values of all available spectrum blocks are calculated, and it is determined whether the second maximum allowable crosstalk threshold is exceeded, and if yes, the connection request is blocked, or if not, a spectrum block with the smallest crosstalk value is selected for spectrum allocation.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0019] To make the content of the present invention clearer and more comprehensible, the present invention is further described in detail below according to specific embodiments of the present invention and the accompanying drawings. Where:

[0020] FIG. 1 is a flowchart of a method for allocating a dedicated protected spectrum based on crosstalk awareness;

[0021] FIG. 2 is a topological graph of an NSFNET according to the present invention;

[0022] FIG. 3 is a schematic diagram of a seven-core optical fiber according to the present invention;

[0023] FIG. 4 shows the structure of a trench-assisted multicore optical fiber according to the present invention;

[0024] FIG. 5 is a schematic diagram of core classification and priority setting of a seven-core optical fiber according to the present invention;

[0025] FIG. 6 is a schematic diagram of spectrum occupation status of cores on working paths according to the present invention; and

[0026] FIG. 7 is a schematic diagram of spectrum occupation status of cores on dedicated protection paths according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiment 1

[0027] As shown in FIG. 1, this embodiment provides a method for allocating a dedicated protected spectrum based on crosstalk awareness, including the following steps: step S1: initializing a space-division multiplexing elastic optical network, and generating a connection request; step S2: calculating a plurality of working paths from a source node to a destination node, and determining whether the working paths are successfully established, where if not, the connection request is blocked, or if yes, the shortest path of the plurality of working paths is selected, a corresponding modulation format is selected according to the shortest path, and a quantity of spectrum slots required for the connection request and a first maximum allowable crosstalk threshold on a fiber optic link are determined according to a bandwidth demand of the connection request and the selected modulation format; step S3: classifying cores according to the quantity of required spectrum slots, setting priorities for the cores, determining whether available spectrum blocks in the cores meet a spectrum consistency constraint and a spectrum continuity constraint, where if not, the connection request is blocked, or if yes, inter-core crosstalk values of all available spectrum blocks are calculated, and it is determined whether the first maximum allowable crosstalk threshold is exceeded, and if yes, the connection request is blocked, or if not, a spectrum block with the smallest crosstalk value is selected for spectrum allocation; step S4: deleting the currently established working paths, calculating a plurality of dedicated protection paths from a source node to a destination node, determining whether the dedicated protection paths are successfully established, where if not, the connection request is blocked, or if yes, the shortest path of the plurality of dedicated protection paths is selected, a corresponding modulation format is selected according to the shortest path, and a quantity of spectrum slots required for the connection request and a second maximum allowable crosstalk threshold on a fiber optic link are determined according to a bandwidth demand of the connection request and the selected modulation format; and step S5: classifying cores according to the quantity of required spectrum slots, setting priorities for the cores, determining whether available spectrum blocks meet a spectrum consistency constraint and a spectrum continuity constraint, where if not, the connection request is blocked, or if yes, inter-core crosstalk values of all available spectrum blocks are calculated, and it is determined whether the second maximum allowable crosstalk threshold is exceeded, and if yes, the connection request is blocked, or if not, a spectrum block with the smallest crosstalk value is selected for spectrum allocation.

[0028] In the method for allocating a dedicated protected spectrum based on crosstalk awareness in this embodiment, in step S1, a space-division multiplexing elastic optical network is initialized, and a connection request is generated. In step S2, a plurality of working paths from a source node to a destination node are calculated, and it is determined whether the working paths are successfully established, where if not, the connection request is blocked, or if yes, the shortest path of the plurality of working paths is selected, to ensure the survivability of each connection request, a corresponding modulation format is selected according to the shortest path, and a quantity of spectrum slots required for the connection request and a first maximum allowable crosstalk threshold on a fiber optic link are determined according to a bandwidth demand of the connection request and the selected modulation format, to help to improve the spectral efficiency of the space-division multiplexing elastic optical network. In step S3, to reduce the generation of spectrum fragments, cores are classified according to the quantity of required spectrum slots, priorities are set for the cores, and it is determined whether available spectrum blocks in the cores meet a spectrum consistency constraint and a spectrum continuity constraint, where if not, the connection request is blocked, or if yes, inter-core crosstalk values of all available spectrum blocks are calculated, and it is determined whether the first maximum allowable crosstalk threshold is exceeded, and if yes, the connection request is blocked, or if not, a spectrum block with the smallest crosstalk value is selected for spectrum allocation. Selection priorities of cores are set, and corresponding cores are designated to carry bandwidth demands of some types, thereby reducing the occupation of spectrum slots with the same number in adjacent cores by services, decreasing an adjacent crosstalk value, helping to flexibly allocate spectrum resources of different cores, and effectively improving the spectrum resource efficiency of the network. In step S4, the currently established working paths are deleted, to help to reduce a crosstalk value, a plurality of dedicated protection paths from a source node to a destination node are calculated, and it is determined that whether the dedicated protection paths are successfully established, where if not, the connection request is blocked, or if yes, the shortest path of the plurality of dedicated protection paths is selected, to ensure the survivability of each connection request, a corresponding modulation format is selected according to the shortest path, and a quantity of spectrum slots required for the connection request and a second maximum allowable crosstalk threshold on a fiber optic link are determined according to a bandwidth demand of the connection request and the selected modulation format, to help to improve the survivability and spectral efficiency of the space-division multiplexing elastic optical network. In step S5, to reduce the generation of spectrum fragments, cores are classified according to the quantity of required spectrum slots, priorities are set for the cores, and it is determined whether available spectrum blocks meet a spectrum consistency constraint and a spectrum continuity constraint, where if not, the connection request is blocked, or if yes, inter-core crosstalk values of all available spectrum blocks are calculated, and it is determined whether the second maximum allowable crosstalk threshold is exceeded, and if yes, the connection request is blocked, or if not, a spectrum block with the smallest crosstalk value is selected for spectrum allocation. In the present invention, the working paths and the dedicated protection paths are established to improve the survivability of the space-division multiplexing elastic optical network, appropriate modulation formats are separately selected for the working paths and the protection paths according to the length of an optical fiber link, and spectrum resources of different cores are flexibly allocated, so that a spectrum allocation scheme is appropriately selected for a connection request, and network resources are optimized, thereby effectively improving the spectrum resource efficiency of the network.

[0029] In the plurality of dedicated protection paths, a spectrum block with the smallest crosstalk value is selected for spectrum allocation. In this case, it indicates that a connection request is successfully established, and subsequently all connection requests are traversed, until the procedure ends. In both the working paths and the dedicated protection paths, if a connection request fails to be established, all the connection requests are traversed, until the procedure ends.

[0030] In step S1, when the space-division multiplexing elastic optical network is initialized, the network is represented by G(E, V, C, F). E={E.sub.1, E.sub.2, . . . , E.sub.|E|−1}, V={V.sub.1, V.sub.2, . . . , V.sub.|V|−1}, C={C.sub.1, C.sub.2, . . . , C.sub.|C|−1}, and F={F.sub.1, F.sub.2, . . . , F.sub.|F|−1} respectively represent sets of links, switch nodes, cores, and available spectrums in the space-division multiplexing elastic optical network. |E|, |V|, |C|, and |F| respectively represent a quantity of optical fiber links, a quantity of switch nodes, a quantity of available cores, and a quantity of spectrum slots in each core in the optical network. (V.sub.i,V.sub.j)∈E. V.sub.i,V.sub.j∈V, representing an optical fiber link from a switch node V.sub.i to a switch node V.sub.j.

[0031] During the generation of a connection request, a group of connection requests are generated. CR represents a set of connection requests. For each connection request CR(s,d,N) in CR, CR(s,d,N)∈CR, s represents a source node of the connection request, d represents a destination node of the connection request, and N represents a required quantity of spectrum slots of the connection request.

[0032] In step S2, during the calculation of the plurality of working paths from the source node to the destination node, the working paths of the connection request are calculated by using a multiple shortest path algorithm. Specifically, a route is calculated for each connection request according to the source node s and the destination node d. When the connection request CR(s,d,N)∈CR arrives, K working paths from the node s to the node d are calculated for the connection request by using a K shortest path algorithm. If the working paths are successfully established, distances of the working paths of the connection request are calculated and are arranged in descending order. K paths with the shortest distances are selected as working paths. If the working paths fail to be established, it is determined that the connection request is blocked.

[0033] The distances of the working paths are calculated. An appropriate modulation format is selected for the working paths of the connection request. A quantity N of spectrum slots required for the connection request and a maximum inter-core crosstalk threshold XT.sub.max.sup.l (dB) allowable on a link l are determined according to a bandwidth demand of the connection request and the selected modulation format.

[0034] In step S3, on the working paths, cores in optical fiber links are first classified according to the quantity of spectrum slots required for the connection request. Such classification of cores can make the use of spectrums more orderly, thereby reducing a quantity of spectrum fragments. Priorities are set for all cores according to the principle of minimizing transmission in adjacent cores, and cores are selected for the connection request according to the priority and class. During the classification of the cores according to the quantity of required spectrum slots and the setting of the priorities for the cores, a core with the highest priority is selected according to the quantity of required spectrum slots for transmission, if a corresponding core fails to be found, a core with a relatively high priority in cores of other types is selected for transmission, if a core still fails to be found, transmission is performed in a public core, and if transmission fails to be performed in a public core, it is determined that the connection request is blocked. Specifically, when CR(s,d,N) arrives, a core with the highest priority is selected according to the quantity N of required spectrum slots for transmission, and a core c.sub.i with the number of i is selected for transmission. If such a core fails to be found, a core with a relatively high priority in cores of other types is selected for transmission. If a core still fails to be found, transmission is performed in a public core, and if transmission fails to be performed in a public core, it is determined that the connection request is blocked.

[0035] On a link l of a working path, all available spectrum blocks that meet a spectrum consistency constraint and a spectrum continuity constraint are selected from the core c.sub.i. Each spectrum block is denoted as S.sub.j,N.sup.il, where j represents a number of a starting spectrum slot, N represents a spectrum slot demand of the connection request, stored in a spectrum block set S.sup.i. If no spectrum block meets requirements, a core with a next priority is selected. If no available spectrum block exists in all cores, it is determined that the connection request is blocked, to help to reduce an inter-core crosstalk value.

[0036] For all spectrum blocks in the set S.sup.i, a crosstalk impact value X.sub.j,N.sup.il of a spectrum slot with the number of j in spectrum blocks S.sub.j,N.sup.il from an adjacent core is calculated according to Formula (1):

[00001] $\begin{matrix} X_{j, N}^{il} = {\begin{matrix} α \times \underset{r \in A}{.Math.} f_{j}^{rl} & \underset{r \in A}{.Math.} f_{j}^{rl} \leq 1 \\ β \times \underset{r \in A}{.Math.} f_{j}^{rl} & \underset{r \in A}{.Math.} f_{j}^{rl} 1 \end{matrix}, & (1) \end{matrix}$

[0037] where α and β are adjustable factors, A represents a set of cores adjacent to c.sub.i. f.sub.j.sup.rl is a binary variable. When a spectrum slot with the number of j in a core r on an optical fiber link l is occupied, f.sub.j.sup.rl=1. When the spectrum slot is not occupied, f.sub.j.sup.rl=0.

[0038] Next, a crosstalk value XT.sub.m.sup.il (the unit is dB) of a spectrum block S.sub.j,N.sup.il is calculated according to Formula (2):

[00002] $\begin{matrix} {XT}_{m}^{il} = 10 \times \lg \frac{n - n \times e^{- (n + 1) \times 2 \times h \times L}}{1 + n \times e^{- (n + 1) \times 2 \times h \times L}} \times \frac{γ + N}{γ + Σ_{j \in {SV}_{m}} X_{j, N}^{il}} & (2) \end{matrix}$ [0039] where n is a quantity of adjacent cores, L is the length of the current link l,

[00003] $h = \frac{2 k^{2} r}{β Λ}$

is an average increase value of inter-core crosstalk in a unit optical fiber length, and k, r, β, and Λ respectively represent a coupling coefficient, a radius of curvature, a propagation coefficient, and a core gap. X.sub.j,N.sup.il is a crosstalk impact value of a j.sup.th spectrum slot on the core c.sub.i on the optical fiber link l by an adjacent core. Σ.sub.j∈sv.sub.mX.sub.j,N.sup.il represents a crosstalk impact value of an m.sup.th candidate spectrum block on the core c.sub.i on the optical fiber link l by an adjacent core; and SV.sub.m represents a set of spectrum slots of an m.sup.th spectrum block, that is, SV.sub.m∈{F.sub.m, F.sub.m+1, . . . , F.sub.m+N−1}.

[0040] XT.sub.m.sup.il is compared with XT.sub.max.sup.l. If XT.sub.m.sup.il≥XT.sub.max.sup.l, S.sub.j,N.sup.il is deleted from S.sup.i. If XT.sub.m.sup.il<XT.sub.max.sup.l, S.sub.j,N.sup.il is kept.

[0041] A crosstalk value XT.sub.m,N on the entire working path is calculated, a spectrum block with the smallest crosstalk value is selected for spectrum allocation, and a set S1 of available spectrum blocks is cleared. Here, XT.sub.m,N=Σ.sub.l∈PXT.sub.m.sup.il, where l is an optical fiber link of a working path P.

[0042] In addition, a method for calculating the inter-core crosstalk values of all the available spectrum blocks is: calculating an impact value between each spectrum block and a spectrum block of an adjacent core; then calculating crosstalk values with all adjacent cores, where if crosstalk values on all links are less than the first maximum allowable crosstalk threshold, spectrum resource allocation schemes are kept, or otherwise, the connection request is blocked; and finally, selecting a scheme with the smallest crosstalk value from all the spectrum resource allocation schemes, and then allocating spectrum resources.

[0043] In step S4, during the calculation of the plurality of dedicated protection paths from the source node to the destination node, the dedicated protection paths of the connection request are calculated by using a multiple shortest path algorithm. Specifically, a route is calculated for each connection request according to the source node s and the destination node d. When the connection request CR(s,d,N)∈CR arrives, the K working paths from the node s to the node d are calculated for the connection request by using a K shortest path algorithm. If the dedicated protection paths are successfully established, distances of the dedicated protection paths of the connection request are calculated and are arranged in descending order. K paths with the shortest distances are selected as the dedicated protection paths. If the dedicated protection paths fail to be established, it is determined that the connection request is blocked.

[0044] The distances of the dedicated protection paths are calculated. An appropriate modulation format is selected for the dedicated protection paths of the connection request. A quantity N of spectrum slots required for the connection request and a maximum inter-core crosstalk threshold XT.sub.max.sup.l (dB) allowable on a link l are determined according to a bandwidth demand of the connection request and the selected modulation format.

[0045] In step S5, on the dedicated protection paths, cores in optical fiber links are first classified according to the quantity of spectrum slots required for the connection request. Such classification of cores can make the use of spectrums more orderly, thereby reducing a quantity of spectrum fragments. Priorities are set for all cores according to the principle of minimizing transmission in adjacent cores, and cores are selected for the connection request according to the priority and class. During the classification of the cores according to the quantity of required spectrum slots and the setting of the priorities for the cores, a core with the highest priority is selected according to the quantity of required spectrum slots for transmission, if a corresponding core fails to be found, a core with a relatively high priority in cores of other types is selected for transmission, if a core still fails to be found, transmission is performed in a public core, and if transmission fails to be performed in a public core, it is determined that the connection request is blocked.

[0046] Moreover, the method for calculating the inter-core crosstalk values of all the available spectrum blocks is: calculating an impact value between each spectrum block and a spectrum block of an adjacent core; then calculating crosstalk values with all adjacent cores, where if crosstalk values on all links are less than the second maximum allowable crosstalk threshold, spectrum resource allocation schemes are kept, or otherwise, the connection request is blocked; and finally, selecting a scheme with the smallest crosstalk value from all the spectrum resource allocation schemes, and then allocating spectrum resources.

[0047] It is determined whether the available spectrum blocks meet the spectrum consistency constraint and the spectrum continuity constraint, if the available spectrum blocks do not meet the spectrum consistency constraint and the spectrum continuity constraint, a core with a next priority is selected, and if none of the cores has an available spectrum block, the connection request is blocked.

[0048] In addition, a method for calculating a crosstalk impact value between adjacent cores is the same as a calculation method on a working path. Therefore, details are not described again.

[0049] In this embodiment, the first maximum allowable crosstalk threshold is the same as the second maximum allowable crosstalk threshold.

[0050] After step S5 is completed, a performance parameter of the network is evaluated according to a quantity of spectrum resources used in the entire network. Specifically, after all connection requests have been processed, the performance parameter of the network is evaluated according to the quantity of spectrum resources used in the entire network.

[0051] After the performance parameter of the network is evaluated, a network status may be further monitored. Specifically, the monitoring of the status of parameter initialization, connection request generation, working path calculation, protection path calculation, modulation format selection, core selection, core classification and priority setting, spectrum resource allocation, spectrum resource release, and network performance evaluation of the space-division multiplexing elastic optical network is mainly completed.

[0052] After the network status is detected, and judgment and early warning further need to be performed on the network. Specifically, coordinated functions between the steps and judgment and early warning functions about whether establishment succeeds in each step are performed, to achieve the objectives of the routing, modulation format, and core and spectrum allocation in the space-division multiplexing elastic optical network, thereby improving the performance of the network and reducing a crosstalk value.

[0053] In this embodiment, a connection request failure represents that a connection request fails.

[0054] Detailed description is provided below with reference to the embodiments.

[0055] As shown in FIG. 2, the network topology of the NSFNET has a total of 14 nodes and 21 bidirectional links. A value on an optical fiber link represents the length of the link, in the unit of km. It is set that a modulation format of each service request is selected Quadrature Phase Shift Keying (QPSK). It is set that a spectrum bandwidth of each link is 200 GHz, a bandwidth of a spectrum slot is 12.5 GHz, that is, each core has a total of 16 spectrum slots, and a seven-core optical fiber is used in each link, as shown in FIG. 3. The seven-core optical fiber uses a trench-assisted structure shown in FIG. 4. The values of the parameters in the optical fiber are respectively k=3.16×10.sup.−5, r=55 (mm), β=4×10.sup.6, and Λ=45 (μm), and

[00004] $h = \frac{2 \times {(3.1 6 \times 1 0^{- 5})}^{2} \times 5 5}{4 \times 1 0^{6} \times 4 5} = 6.1 \times 1 0^{- 1 3} .$

[0056] It is assumed that a connection request CR.sub.1(s,d,N) is generated, where s=2, d=11, and N=2. It is set that K=3. A selected working path is 2-5-12-11. According to the length of each link, links l.sub.1, l.sub.2, and l.sub.3 respectively represent optical fiber links (2, 5), (5, 12), and (12,11). QPSK is selected as a modulation format for the three optical fiber links. Therefore, the N value of the connection request on l.sub.1, l.sub.2, and l.sub.3 is 2. A maximum allowable crosstalk value of each link is XT.sub.max.sup.1=XT.sub.max.sup.2=XT.sub.max.sup.3=−18 (dB). As shown in FIG. 3, the number of a seven-core optical fiber is represented by digits. The seven-core optical fiber is classified according to the N value of a service, and a priority is set for each optical fiber. As shown in FIG. 5, for a connection request of N=2, transmission is preferentially performed in a No. 1 core. For a connection request of N=3, transmission is preferentially performed in a No. 3 core. For a connection request of N=4, transmission is preferentially performed in a No. 5 core. When the cores cannot satisfy transmission requirements, transmission is performed in a No. 7 core. When CR.sub.1(2, 11, 2) arrives, a core c.sub.1 is preferentially selected on the links l.sub.1, l.sub.2, and l.sub.3. Searches are performed from the smallest spectrum slot number to the largest spectrum slot number on c.sub.1 to find all available spectrum blocks that meet a spectrum continuity constraint condition and a spectrum consistency constraint condition.

[0057] When CR.sub.1(2, 11, 2) arrives, spectrum occupation status of the core c.sub.1 and four adjacent cores are shown in FIG. 6. The gray color represents that a spectrum slot has been occupied. According to the spectrum continuity constraint and the spectrum consistency constraint, a set of selectable spectrum blocks in the core c.sub.1 is S.sup.1={S.sub.3,2.sup.1, S.sub.4,2.sup.1, S.sub.15,2.sup.1}. It is set that α=0.5, β=3, and γ=1. On the link l.sub.1, the length of the optical fiber link is 1300 (km), X.sub.3,2.sup.11=3×3+0.5×1=9.5, and XT.sub.3,2.sup.11=

[00005] $1 0 \times l g \frac{3 - 3 \times e^{- 4 \times 2 \times 6.1 \times 1 0^{- 1 3}} \times 1 3 0 0}{1 + 3 \times e^{- 4 \times 2 \times 6.1 \times 1 0 - 1 3} \times 1 3 0 0} \times \frac{1 + 2}{1 + 9.5} = - 2 3.7 7 9 (d B);$

X.sub.4,2.sup.11=0.5×1+0.5×1=1, and

[00006] $X T_{4, 2}^{1 1} = 1 0 \times l g \frac{3 - 3 \times e^{- 4 \times 2 \times 6.1 0 \times 1 0^{- 13}} \times 1 3 0 0}{1 + 3 \times e^{- 4 \times 2 \times 6.1 0 \times 1 0^{- 1 3}} \times 1 3 0 0} \times \frac{1 + 2}{1 + 1} = - 1 2 4.8 3 9 (d B);$

X.sub.15,2.sup.11=3×2+0.5×1=6.5,

[00007] $X T_{15, 2}^{1 1} = 1 0 \times l g \frac{3 - 3 \times e^{- 4 \times 2 \times 6.1 0 \times 1 0^{- 1 3}} \times 1 3 0 0}{1 + 3 \times e^{- 4 \times 2 \times 6.1 0 \times 1 0^{- 1 3}} \times 1 3 0 0} \times \frac{1 + 2}{1 + 6.5} = - 3 3.2 90 (d B) .$

All the values are less than the maximum allowable crosstalk value. Similarly, on the link l.sub.2, the length of the link is 1400 (km). X.sub.3,2.sup.12=15, and XT.sub.3,2.sup.12=−15.544 (dB) is greater than a crosstalk value. Therefore, the spectrum block S.sub.3,2.sup.1 is deleted from S.sup.1, and S.sup.1={S.sub.4,2.sup.1, S.sub.15,2.sup.1}; X.sub.4,2.sup.12=6.5, XT.sub.4,2.sup.12=−33.162 (dB); and X.sub.15,2.sup.12=0.5, XT.sub.15,2.sup.12=−165.808 (dB). On the link l.sub.3, the length of the link is 300 (km), X.sub.4,2.sup.13=6.5, XT.sub.15,2.sup.12=−89.594 (dB); and X.sub.5,2.sup.12=1, and XT.sub.15,2.sup.12=−134.391 (dB). Therefore, XT.sub.4,2.sup.1=XT.sub.4,2.sup.13+XT.sub.4,2.sup.12+XT.sub.4,2.sup.13=−247.595 (dB) and XT.sub.15,2=XT.sub.15,2.sup.11+XT.sub.15,2.sup.12+XT.sub.15,2.sup.13=−333.489 (dB). Therefore, the spectrum block S.sub.15,2.sup.1 with the smallest total crosstalk value is selected. That is, two spectrum slots with the number of 15 and the number of 16 are selected.

[0058] Next, a dedicated protection path 2-1-7-9-11 is established for CR.sub.1(2,11,2). According to the length of the link, QPSK is selected as the modulation format for the four links l.sub.1 (2,1), l.sub.2 (1,7), l.sub.3 (7,9), and l.sub.4 (9,11) on the dedicated protection path. Therefore, the N value of the connection request on l.sub.1, l.sub.2, l.sub.3, and l.sub.4 is 2. A maximum allowable crosstalk value of each link is XT.sub.max.sup.1=XT.sub.max.sup.2=XT.sub.max.sup.3=XT.sub.max.sup.4=−18 (dB). The core c.sub.4 is selected for transmission. It is set when CR.sub.1(2, 11, 2) arrives, the spectrum status of the core c.sub.4 and adjacent cores thereof on the link are shown in FIG. 7. The gray color represents that the spectrum slot has been occupied. According to the spectrum continuity constraint and the spectrum consistency constraint, a set of selectable spectrum blocks is S.sup.4={S.sub.7,2.sup.4,S.sub.11,2.sup.4,S.sub.12,2.sup.4}. It is set that α=0.5, β=3, and γ=1, the link length on the link l.sub.1 is 1250 (km), XT.sub.7,2.sup.41=6.5, XT.sub.7,2.sup.41=−33.358 (dB), XT.sub.11,2.sup.41=0.5, XT.sub.11,2.sup.41=−166.792 (dB), and X.sub.12,2.sup.41=0.5, XT.sub.12,2.sup.42=−166.792 (dB). On the link l.sub.2, the length of the optical fiber link is 1450 (km), X.sub.7,2.sup.42=12, XT.sub.7,2.sup.42=−19.010 (dB), X.sub.11,2.sup.42=0.5, XT.sub.7,2.sup.42=−165.503 (dB), and X.sub.12,2.sup.42=0.5, and XT.sub.12,2.sup.42=−165.503 (dB). On the link l.sub.3, X.sub.12,2.sup.43=12, XT.sub.12,2.sup.43=−19.826 (dB), X.sub.11,2.sup.43=0.5, XT.sub.11,2.sup.43=−171.828 (dB), and X.sub.12,2.sup.43=6.5, and XT.sub.12,2.sup.43=−34.366 (dB). On the link l.sub.4, X.sub.7,2.sup.44=6.5, XT.sub.7,2.sup.44=−33.350 (dB), X.sub.11,2.sup.44=1, XT.sub.11,2.sup.44=−125.063 (dB), and X.sub.12,2.sup.44=6.5, and XT.sub.12,2.sup.44=−34.950 (dB). The crosstalk values of all spectrum blocks meet requirements, and therefore S.sup.4={S.sub.7,2.sup.4, S.sub.11,2.sup.4,S.sub.12,2.sup.4}. XT.sub.7,2=XT.sub.7,2.sup.41+XT.sub.7,2.sup.42+XT.sub.7,2.sup.43+XT.sub.7,2.sup.44=−105.544 (dB), XT.sub.11,2=XT.sub.11,2.sup.41+XT.sub.11,2.sup.42+XT.sub.11,2.sup.43+XT.sub.11,2.sup.44=−628.986 (dB) and XT.sub.12,2=XT.sub.12,2.sup.41+XT.sub.12,2.sup.42+XT.sub.12,2.sup.43+XT.sub.12,2.sup.44=−401.611 (dB). The spectrum block S.sub.11,2.sup.4 with the smallest total crosstalk value is selected. That is, two spectrum slots with the number of 11 and the number of 12 are selected.

[0059] The connection request CR.sub.1(2, 11, 2) is successfully established. A process of establishing another connection request is similar to that above.

Embodiment 2

[0060] Based on the same inventive concept, the present invention provides a system for allocating a dedicated protected spectrum based on crosstalk awareness. The principle of solving the problems is similar to that of the method for allocating a dedicated protected spectrum based on crosstalk awareness. Details are not repeated.

[0061] This embodiment provides a system for allocating a dedicated protected spectrum based on crosstalk awareness, including: [0062] a connection request module, configured to: initialize a space-division multiplexing elastic optical network, and generate a connection request; [0063] a working path establishment module, configured to: calculate a plurality of working paths from a source node to a destination node, and determine whether the working paths are successfully established, where if not, the connection request is blocked, or if yes, the shortest path of the plurality of working paths is selected, a corresponding modulation format is selected according to the shortest path, and a quantity of spectrum slots required for the connection request and a first maximum allowable crosstalk threshold on a fiber optic link are determined according to a bandwidth demand of the connection request and the selected modulation format; [0064] a core classification module, configured to: classify cores according to the quantity of required spectrum slots, set priorities for the cores, determine whether available spectrum blocks in the cores meet a spectrum consistency constraint and a spectrum continuity constraint, where if not, the connection request is blocked, or if yes, inter-core crosstalk values of all available spectrum blocks are calculated, and it is determined whether the first maximum allowable crosstalk threshold is exceeded, and if yes, the connection request is blocked, or if not, a spectrum block with the smallest crosstalk value is selected for spectrum allocation; [0065] a dedicated protection path establishment module, configured to: delete the currently established working paths, calculate a plurality of dedicated protection paths from a source node to a destination node, determine whether the dedicated protection paths are successfully established, where if not, the connection request is blocked, or if yes, the shortest path of the plurality of dedicated protection paths is selected, a corresponding modulation format is selected according to the shortest path, and a quantity of spectrum slots required for the connection request and a second maximum allowable crosstalk threshold on a fiber optic link are determined according to a bandwidth demand of the connection request and the selected modulation format; and [0066] a spectrum allocation module, configured to: classify cores according to the quantity of required spectrum slots, set priorities for the cores, determine whether available spectrum blocks meet a spectrum consistency constraint and a spectrum continuity constraint, where if not, the connection request is blocked, or if yes, inter-core crosstalk values of all available spectrum blocks are calculated, and it is determined whether the second maximum allowable crosstalk threshold is exceeded, and if yes, the connection request is blocked, or if not, a spectrum block with the smallest crosstalk value is selected for spectrum allocation.

[0067] A person skilled in the art should understand that the embodiments of the present application may be provided as a method, a system or a computer program product. Therefore, the present application may use a form of hardware only embodiments, software only embodiments, or embodiments with a combination of software and hardware. Moreover, the present application may use a form of a computer program product that is implemented on one or more computer-usable storage media (including but not limited to a disk memory, a CD-ROM, an optical memory, and the like) that include computer usable program code.

[0068] The present application is described with reference to the flowcharts and/or block diagrams of the method, the device (system), and the computer program product according to the embodiments of the present application. It should be understood that computer program instructions may be used to implement each process and/or each block in the flowcharts and/or the block diagrams and a combination of a process and/or a block in the flowcharts and/or the block diagrams. These computer program instructions may be provided for a general-purpose computer, a dedicated computer, an embedded processor, or a processor of any other programmable data processing device to generate a machine, so that the instructions executed by a computer or a processor of any other programmable data processing device generate an apparatus for implementing a specific function in one or more processes in the flowcharts and/or in one or more blocks in the block diagrams.

[0069] These computer program instructions may be stored in a computer-readable memory that can instruct the computer or any other programmable data processing device to work in a specific manner, so that the instructions stored in the computer-readable memory generate an artifact that includes an instruction apparatus. The instruction apparatus implements a specific function in one or more processes in the flowcharts and/or in one or more blocks in the block diagrams.

[0070] These computer program instructions may be loaded onto a computer or another programmable data processing device, so that a series of operations and steps are performed on the computer or the another programmable device, thereby generating computer-implemented processing. Therefore, the instructions executed on the computer or the another programmable device provide steps for implementing a specific function in one or more processes in the flowcharts and/or in one or more blocks in the block diagrams.

[0071] Obviously, the foregoing embodiments are merely examples for clear description, rather than a limitation to implementations. For a person of ordinary skill in the art, other changes or variations in different forms may also be made based on the foregoing description. All implementations cannot and do not need to be exhaustively listed herein. Obvious changes or variations that are derived there from still fall within the protection scope of the invention of the present invention.

METHOD AND SYSTEM FOR ALLOCATING DEDICATED PROTECTED SPECTRUM BASED ON CROSSTALK AWARENESS

Inventors

Cpc classification

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H04Q2011/0086

ELECTRICITY

Classification Explorer

H04Q2011/0049

ELECTRICITY

Classification Explorer

H04B10/032

ELECTRICITY

Classification Explorer

H04Q11/0005

ELECTRICITY

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H04Q11/0062

ELECTRICITY

International classification

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H04Q11/00

ELECTRICITY

Classification Explorer

H04B10/032

ELECTRICITY

Abstract

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Description