Survivability multipath resource allocation method based on fragment awareness in multicore fiber

Abstract

The present application relates to a kind of survival multipath resource allocation methods based on fragment perception in multicore optical fiber, belong to optical fiber communication and optical transport network field.The present application transmits service by using survival multipath and the routing of spectrum fragmentation metric-based, core selection and spectrum allocation method, when service reaches space division multiplexing elastic optical network, select two transmission paths that can guarantee the survival of service, if two paths do not satisfy service transmission rate, sub-service is transmitted on three paths by dividing service into smaller sub-service;Design spectrum fragmentation sensitive path fragmentation rate formula, according to path fragmentation rate formula, select the core in each path of selected path combination maximum path fragmentation rate;Respectively in each path of selected path combination, select the spectral block in selected core with the minimum difference and less than inter-core crosstalk threshold of the spectral block required by service on the path. The method reduces the bandwidth blocking rate of service in space division multiplexing elastic optical network and improves spectrum utilization.

Description

Technical Field

[0001] This invention belongs to the field of optical fiber communication and optical transmission networks, and relates to a fragment-aware survivable multipath resource allocation method in multi-core optical fibers. Background Technology

[0002] With the rapid development of new technologies and applications such as cloud computing and big data, optical networks need to continuously improve their flexible and dynamic transmission capabilities to adapt to complex and ever-changing real-world network conditions. This has led to the emergence of new optical transport network architectures such as Elastic Optical Networks (EONs) based on Orthogonal Frequency Division Multiplexing (OFDM). EONs effectively overcome the shortcomings of traditional Wavelength Division Multiplexing (WDM) networks, such as their coarse-grained bandwidth resource allocation and fixed modulation formats, making more efficient use of optical transport network resources. EONs can divide the spectrum resources in the network into fine-grained and continuous frequency slots (FS) according to the bandwidth requested by the service, serving requests in a manner closer to a meshless system, greatly reducing bandwidth consumption. Due to the continuous rapid growth of network traffic and the limitations of nonlinear effects in optical fibers, the transmission capacity of single-mode fiber (SMF) is approaching the Shannon limit. To meet the ever-growing demand for optical network bandwidth, Space Division Multiplexing Elastic Optical Networks (SDM-EONs), which combine elastic optical networks with space division multiplexing (SDM) technology, can effectively address the high-capacity requirements of current optical networks. Among them, SDM-EONs, which incorporate multi-core fiber (MCF), are considered one of the most promising next-generation optical transport network technologies.

[0003] Space division multiplexing (SDM) technology significantly improves the transmission capacity of optical fibers by introducing spatial dimensions, but the introduction of fiber cores also brings some unavoidable problems. With the increase in transmission capacity, the network's capacity to handle service requests increases, leading to more frequent optical path splitting and reconstruction due to the dynamic arrival and departure of services. This dynamic splitting and reconstruction results in a large amount of spectral fragmentation on the optical fibers in the network. Excessive spectral fragmentation on the fibers leads to a significant reduction in the number of available frequency slots, severely impacting the connection of upcoming services and ultimately causing a sharp deterioration in network performance. Furthermore, when the same frequency slots of adjacent fiber cores are occupied, physical impairments to the transmission signal occur, such as significant inter-core crosstalk (XT), which severely affects the transmission quality of service requests. Therefore, to fully utilize the high-capacity transmission and flexible resource allocation characteristics of SDM flexible optical networks, it is crucial to address the routing, spectrum, and core assignment (RSCA) issues for incoming services.

[0004] With the continuous development of optical network technology, the transmission capacity of a single optical fiber can reach 400Gbps or even over 1Tbps. The use of spatial division multiplexing (SDM) technology has significantly increased the transmission capacity of traditional resilient optical networks, enabling them to support massive amounts of diverse services. However, link or node failures in the network can cause substantial data loss and service interruptions, resulting in incalculable losses for users and operators. Therefore, it is essential to study the survivability of SDM-EONs and the spectrum fragmentation problem caused by the dynamic allocation and release of spectrum resources. Summary of the Invention

[0005] In view of this, the purpose of this invention is to provide a fragment-aware survivability multipath resource allocation method in multi-core optical fibers to reduce network bandwidth congestion rate, spectrum fragmentation rate and improve spectrum utilization.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A fragment-aware, survivable multipath resource allocation method for multi-core optical fibers includes the following steps:

[0008] S1. Initialize the spatial multiplexing elastic optical network, determine the remaining spectrum resources of the current elastic optical network, and set the inter-core crosstalk threshold XT. th ;

[0009] S2. Based on the source node s, destination node d, required transmission rate B, and protection ratio q of the service request, Dijkstra's algorithm is used in the spatial multiplexing elastic optical network topology to find the shortest path between the service source and destination nodes, and the link of the shortest path is deleted from the network topology.

[0010] Repeat step S2 until K disjoint shortest paths are found and stored in the shortest path set P; where K is a maximum integer value of the average node degree of the space-division multiplexing elastic optical network.

[0011] S3. Determine the number of paths in the shortest path set P: If the number of paths is less than 2, block the service request; if the number of paths is greater than or equal to 2, combine the paths in the shortest path set P into path combinations and store them in the candidate path combination set C. p middle;

[0012] S4. From the candidate path combination set C p If a path combination containing two paths can be selected, and a spectrum block that meets the number of frequency slots required for the service to be transmitted on the selected path can be found in the candidate path combination containing only two paths, then the two-path transmission strategy is adopted to transmit the service; otherwise, the service is divided into smaller sub-services and the three-path transmission strategy is adopted to transmit the service.

[0013] S5. Calculate the path fragmentation rate of each fiber core on each path in the selected path combination according to the path fragmentation rate formula, and select the fiber core in the path through the path fragmentation sensing strategy; on each path of the selected candidate path combination, use the spectrum allocation strategy based on spectrum and crosstalk sensing to allocate the spectrum block with the smallest difference from the spectrum block required by the service and less than the crosstalk threshold.

[0014] Furthermore, in step S3, if the number of paths in the shortest path set P is greater than or equal to 3, then the first three paths in P are combined in pairs to obtain P. n n = 1, 2, 3, and according to P n The candidate path combinations are stored in ascending order of their total lengths in the set C. p In the sequence {P1,P2,P3,P4}, P4 represents a combination of three paths contained in P.

[0015] If the shortest path set P contains only two paths, then the combination of the two paths is stored in the candidate path combination set C. p ={P1} in.

[0016] Further, step S4 includes the following steps:

[0017] S41. Determine the candidate path combination set C p Is it empty? If C pIf not empty, proceed to step S42; if C p If empty, the business request will be blocked;

[0018] S42, If the candidate path combination set C p If all two-path combination transmissions fail, then the three-path combination P4 transmission service is used, and the process proceeds to step S44.

[0019] Otherwise, proceed sequentially from set C p Select candidate path combination P n Where n = 1, 2, 3, a two-path combined transmission strategy is adopted for service transmission, and then proceed to step S43;

[0020] S43. Based on the required transmission rate and protection ratio of the service, calculate the number of frequency slots required on each path when the service is transmitted on the two-path combination; if the maximum free spectrum block on each path in the selected path combination meets the number of frequency slots required for the service to be transmitted on that path, then execute the fiber core selection strategy and proceed to step S5; otherwise, select from set C. p Delete the path combination and return to step S41;

[0021] S44, From set C p Select candidate path combination P4, and calculate the number of frequency slots required on each path when the service is transmitted on the three paths according to the service transmission rate and protection ratio; if the maximum spectrum block on any path does not meet the number of frequency slots required for service transmission, then block the service request; otherwise, execute the fiber core selection strategy and proceed to step S5.

[0022] Furthermore, in step S43, when the service uses a two-path combined transmission, the number of frequency slots required on each path is:

[0023]

[0024] In the formula, R i This represents the i-th business request; This indicates that when the business request R... i The number of frequency slots required on each path; B represents the service transmission rate in Gbps; q×B represents the service transmission rate under the condition of satisfying the service protection ratio q; B fs M represents the bandwidth provided per unit bandwidth; i Indicates business request R i The modulation format level; GB indicates the number of guard bands.

[0025] In step S44, when the service is transmitted on the first two paths of candidate path combination P4, the required number of frequency slots is:

[0026]

[0027] When the service is transmitted on the third path of candidate path combination P4, the required number of frequency slots is:

[0028]

[0029] In the formula This indicates that when the business request R... i The number of bandwidths required for transmission on the first two paths of candidate path combination P4. This indicates that when the business request R... i The number of bandwidths required for transmission on the third path of candidate path combination P4.

[0030] Further, step S5 includes the following steps:

[0031] S51. According to the graph vertex coloring theory, the non-adjacent fiber cores on each path are grouped into high-priority fiber core group, secondary-priority fiber core group and low-priority fiber core group. The ratio of the number of fiber cores in the three groups is 3:3:1.

[0032] S52. Based on the path fragmentation rate formula, calculate the path fragmentation rate of the high-priority fiber core group, the second-priority fiber core group, and the low-priority fiber core group on each path in the selected path combination. Sort each group of fiber cores in the path in descending order of its path fragmentation rate and store them in the candidate fiber core set C. sort middle;

[0033] S53, Determine Set C sort Is it empty? If it is empty, return to step S4; if it is not empty, select the fiber core with the highest path fragmentation rate.

[0034] S54. Store all available spectrum blocks in the selected fiber core into the available spectrum block set FB. available In, and for the set FB available The available spectrum blocks are arranged in non-descending order according to the number of frequency slots; the available spectrum blocks represent the spectrum blocks in the path that satisfy the number of frequency slots required for service transmission.

[0035] S55, Determine the set FB available Is it empty? If empty, then select from the candidate fiber core set C. sort Delete the selected fiber core and return to step S53; if not empty, retrieve from set FB. available Select the first spectrum block and proceed to step S56;

[0036] S56. Calculate the inter-core crosstalk value XT generated when the service is allocated to the selected spectrum block; if the inter-core crosstalk value XT is less than the inter-core crosstalk threshold XT th If the selected spectrum block is selected, it will be assigned to the service; otherwise, it will be selected from the set FB.available Delete the selected spectrum block and return to step S55.

[0037] Furthermore, in step S52, the path fragmentation rate formula is specifically as follows:

[0038]

[0039] In the formula, Θ c Indicates the path fragmentation rate on fiber core c; FB i This represents the number of frequency slots contained in the i-th free spectrum block in the path; This represents the number of available free spectrum blocks in the i-th path.

[0040] In step S56, the inter-core crosstalk value is calculated as follows:

[0041]

[0042] In the formula, n represents the number of fiber cores adjacent to the selected fiber core; L represents the length of the fiber core for service transmission; and h represents the average increase in crosstalk per unit length in the fiber core.

[0043]

[0044] Where ε represents the coupling coefficient, r represents the bending radius, β represents the propagation constant, and ω tr Indicates the fiber core spacing.

[0045] The beneficial effects of this invention are as follows: This invention simultaneously considers network survivability and the spectrum fragmentation problem in the network. By designing a path selection transmission strategy based on survivability multipath protection, when a service fails to be transmitted on two paths, the bandwidth blocking rate is reduced by dividing the service into smaller sub-services and transmitting them on three paths. In addition, a fiber core selection method and spectrum allocation strategy based on path fragmentation rate are designed to reserve more and more continuous spectrum blocks for subsequent services, reduce the bandwidth blocking rate of services, and improve the utilization rate of network spectrum resources.

[0046] Other advantages, objectives, and features of the invention will be set forth in part in the description which follows, and in part will be apparent to those skilled in the art from the following examination, or may be learned from practice of the invention. The objectives and other advantages of the invention can be realized and obtained through the following description. Attached Figure Description

[0047] To make the objectives, technical solutions, and advantages of the present invention clearer, the preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings, wherein:

[0048] Figure 1A diagram illustrating survivable multipath routing;

[0049] Figure 2 This is a schematic diagram of fiber core selection and spectrum allocation based on path fragmentation rate, where (a) shows the resource allocation of fiber cores in the high-priority fiber core group in the path before service allocation, and (b) shows the spectrum blocks allocated to services.

[0050] Figure 3 This is a flowchart illustrating the specific process of the method of the present invention. Detailed Implementation

[0051] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of the present invention. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0052] The accompanying drawings are for illustrative purposes only and are schematic diagrams, not actual pictures. They should not be construed as limiting the invention. To better illustrate the embodiments of the invention, some parts in the drawings may be omitted, enlarged, or reduced, and do not represent the actual product dimensions. It is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings.

[0053] In the accompanying drawings of the embodiments of the present invention, the same or similar reference numerals correspond to the same or similar components. In the description of the present invention, it should be understood that if terms such as "upper," "lower," "left," "right," "front," and "rear" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, they are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the terms used to describe positional relationships in the drawings are only for illustrative purposes and should not be construed as limiting the present invention. For those skilled in the art, the specific meaning of the above terms can be understood according to the specific circumstances.

[0054] like Figure 1The diagram illustrates survivable multipath routing, showing the slot status among three non-intersecting candidate paths selected by a service. Each square represents a slot, with different line shapes indicating different slot statuses. The number above each square represents its index. Each row of consecutive slots represents the slot status on different paths. Gray grid lines indicate slots occupied by established services, while white lines indicate idle slots. It is assumed that all three paths use Binary Phase Shift Keying (BPSK) modulation. On path 1, the frequency slots with index values ​​[FS1, FS4], [FS7, FS8], and [FS12, FS16] are available idle frequency slots, while the remaining frequency slots are occupied by established services. On path 2, the frequency slots with index values ​​FS5, [FS8, FS11], and [FS14, FS16] are available idle frequency slots, while the remaining frequency slots are unavailable. On path 3, the frequency slots with index values ​​[FS1, FS4], [FS7, FS8], and [FS11, FS1] are available idle frequency slots, while the remaining frequency slots are unavailable.

[0055] Assuming a service transmission rate of 125Gbps and a protection ratio q = 0.8, the formula for calculating the number of frequency slots required on each path when using a two-path combined transmission is:

[0056]

[0057] In the formula, R i This represents the i-th business request; This indicates that when the business request R... i The number of frequency slots required on each path when transmitting over a two-path combination; B represents the service transmission rate, in Gbps; q×B represents the service transmission rate under the condition of satisfying the service protection ratio q, which generally ranges from 0.5. <q<1;B fs This represents the bandwidth provided per unit bandwidth, with a value of 12.5 GHz; M i Indicates business R i The modulation format level; GB indicates the number of guard bands, which is generally taken as 1.

[0058] In this example, the parameters B = 125Gbps, q = 0.8, and B... fs =12.5GHz and M i Substituting 1 into the formula for the number of frequency slots required for a path in a two-path combined transmission, we obtain... Therefore, when transmitting on two paths, 8 frequency slots should be allocated for the service. However, the maximum number of frequency slots in the largest free spectrum block on the three candidate paths is 4, which does not meet the required number of frequency slots for the service to be transmitted on that path (for simplicity, guard slots are not considered). In this case, consider transmitting the service on three paths. When the service is transmitted on the first two paths of the three-path combination, the required number of frequency slots is calculated using the following formula:

[0059]

[0060] And when the service is transmitted on the third path of the three-path combination, the required number of frequency slots is calculated as follows:

[0061]

[0062] Given B = 125 Gbps, q = 0.8, and B... fs =12.5GHz and M i Substituting 1 into equations (2) and (3) respectively, we get In a three-path combined transmission, each path should be allocated 4 frequency slots for the service (for simplicity, guard slots are not considered). Figure 1 The candidate path combination shown can meet the number of bandwidths required when a service selects this path combination for transmission.

[0063] like Figure 2 The diagram illustrates fiber core selection and spectrum allocation based on path fragmentation rate. Figure 2 (a) This shows the resource allocation of the three fiber cores in the high-priority fiber core group on Path 1 before service allocation. Specifically, on fiber core 1, the frequency slots with index values ​​[FS1, FS2], [FS6, FS8], and [FS13, FS15] are available idle frequency slots, while the remaining slots are occupied by established services. On fiber core 3, the frequency slots with index values ​​[FS1, FS4], [FS7, FS8], and [FS12, FS16] are available idle frequency slots, while the remaining slots are unavailable. On fiber core 5, the frequency slots with index values ​​[FS1, FS4] and [FS8, FS13] are available idle frequency slots, while the remaining slots are unavailable. The path fragmentation rate for each fiber core is calculated using the following formula:

[0064]

[0065] Θ c Indicates the path fragmentation rate on fiber core c; FB i This represents the number of frequency slots contained in the i-th free spectrum block in the path; This represents the number of available free spectrum blocks in the i-th path.

[0066] For fiber core 1, the parameters FB1 = 2FS, FB2 = 3FS, FB3 = 3FS, substituting into equation (4) yields Similarly, the parameters in fiber core 3 FB1 = 4FS, FB2 = 2FS, FB3 = 5FS, substituting into equation (4) yields Parameters of fiber core 5 FB1 = 4FS, FB2 = 6FS, substituting into equation (4) yields Compare the path fragmentation rates of the three fiber cores, Θ1 > Θ3 > Θ5, and store them in descending order in the candidate fiber core set C. sort In the sequence {c1, c3, c5}, fiber core 1 with the highest path fragmentation rate is selected as the transmission path for the service. However, the maximum spectrum block size on fiber core 1 is 3, which does not meet the number of frequency slots required for service transmission on this path. Therefore, fiber core 3 with the highest path fragmentation rate is selected next. At this time, the available frequency slots on the fiber core are FB1 = 4FS and FB3 = 5FS. The available spectrum blocks on the fiber core are sorted in non-descending order and stored in the available spectrum block set FB. available In this process, the set of available spectrum blocks FB is obtained. available ={FB1, FB3}, therefore, the spectrum block FB1 = 4FS that is closest to the number of frequency slots required by the service is selected as the transmission spectrum block, as shown in the attached figure. Figure 2 As shown in (b). Finally, it is calculated whether the inter-core crosstalk value generated when selecting this spectrum block is less than the set inter-core crosstalk threshold. The formula for calculating the inter-core crosstalk value is as follows:

[0067]

[0068] In the formula, n represents the number of fiber cores adjacent to the selected fiber core; L represents the length of the fiber core for service transmission; and h represents the average increase in crosstalk per unit length in the fiber core.

[0069]

[0070] Where ε represents the coupling coefficient, r represents the bending radius, β represents the propagation constant, and ω tr Indicates the fiber core spacing.

[0071] The following is combined Figure 3 The present invention describes a fragment-aware survivability multipath resource allocation method for multi-core optical fibers, specifically comprising the following steps:

[0072] S1. Initialize the spatial multiplexing elastic optical network, determine the remaining spectrum resources of the current elastic optical network, and set the inter-core crosstalk threshold XT. thIf a new service request R = (s,d,B,q) arrives at SDM-EONs, proceed to step S2; where s,d,B,q represent the source node, destination node, transmission rate, and protection ratio of the service request, respectively.

[0073] S2. Based on the source and destination nodes of the service request, execute Dijkstra's algorithm to search for the shortest path between the source and destination nodes in SDM-EONs, and delete the link of the shortest path from the network topology; repeat the above process until at most K non-intersecting shortest paths are found, and store them in the shortest path set P, where K is a maximum integer value of the average node degree of the network topology of SDM-EONs.

[0074] S3. If the number of paths in set P is less than two, then block the service request; otherwise, proceed to step S4.

[0075] S4. If the number of paths in set P is greater than three, then combine the first three paths in set P in pairs to obtain P. n n = 1, 2, 3, and according to P n The lengths are sorted in ascending order and stored in the candidate path combination set C. p ={P1,P2,P3,P4}, where P4 is a combination of three paths contained in set P;

[0076] If set P contains only two paths, then combine them and store them in set C. p ={P1} in.

[0077] S5, Determine set C p Is it empty? If it is empty, block the service request; otherwise, proceed to step S6.

[0078] S6. Determine whether all two-path combination allocation methods have been tried; if all two-path combination transmissions fail, adopt the three-path combination transmission strategy and proceed to step S7; otherwise, adopt the two-path combination transmission strategy and proceed to step S8.

[0079] S7, from set C p Select candidate path combination P4, and calculate the number of frequency slots required on each path when the service adopts three-path combination transmission according to equations (2) and (3), and proceed to step S9.

[0080] S8, from set C p Select candidate path combination P n Calculate the number of frequency slots required on each of the two paths when the service adopts a two-path combined transmission according to formula (1), and proceed to step S9.

[0081] S9. Determine if the largest free spectrum block on the path contains a spectrum block that meets the number of frequency slots required for service transmission; if it meets the number of frequency slots required for service transmission, proceed to step S10; if not, remove the spectrum block from set C. p Delete the path combination and return to step S5.

[0082] S10. On each selected path, according to the graph vertex coloring theory, the non-adjacent fiber cores on each path are grouped into a group. Generally, 7-core fiber is used. The 7-core fiber can be divided into three groups. The fiber cores on each path are divided into high-priority fiber core group, secondary-priority fiber core group and low-priority fiber core group. The ratio of the number of fiber cores in the three fiber core groups is 3:3:1.

[0083] S11. Based on the fragmentation-sensitive path fragmentation rate formula, calculate the path fragmentation rate of each group of fiber cores on each path in the selected path combination, and store them in the path fragmentation rate set Θ. c ={Θ1,Θ2,…Θ n}middle.

[0084] S12, arrange the fiber core according to the calculated path breakage rate Θ c After being sorted in descending order, they are stored in the candidate fiber core set C. sort middle.

[0085] S13, Determine set C sort Is it empty? If empty, delete the selected candidate path combination and return to step S5; if not empty, select C. sort Mid-path fragmentation rate Θ c For the fiber core with the maximum value, proceed to step S14.

[0086] S14. Store the available free spectrum blocks in the selected fiber core into the available spectrum block set FB. available In the middle, for the set FB available All available spectrum blocks are sorted in non-descending order by the number of frequency slots.

[0087] S15, Determine FB available Is the set empty? If it is empty, then in C... sort Delete the selected fiber core and return to step S13; otherwise, remove the fiber core from set FB. available Select the first spectrum block and proceed to step S16.

[0088] S16. Calculate the inter-core crosstalk value XT generated when the service is allocated to the selected spectrum block according to formula (5); determine whether the generated inter-core crosstalk value is less than the inter-core crosstalk threshold XT. th If the value is less than XT, the resource allocation is successful, and the current resource allocation ends; if the value is greater than XT... th Then in the set FB available Delete the spectrum block and return to step S15.

[0089] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for survivable multipath resource allocation based on fragmentation awareness in multi-core optical fibers, characterized by: The method comprises the following steps: S1, initializing the space division multiplexing elastic optical network, determining the current elastic optical network residual spectrum resource, setting the inter-core crosstalk threshold XT th ; S2, according to the source node s, the destination node d, the required transmission rate B and the protection ratio q of the service request, the Dijkstra algorithm is used to find the shortest path between the source node and the destination node in the space division multiplexing elastic optical network topology, and the link of the shortest path is deleted from the network topology; Repeat step S2 until K non-intersecting shortest paths are found and stored in the shortest path set P; wherein K is the maximum integer of the average node degree of the space division multiplexing elastic optical network; S3, judging the number of paths in the shortest path set P: if the number of paths is less than 2, blocking the service request; if the number of paths is greater than or equal to 2, forming path combinations from the paths in the shortest path set P and storing the path combinations in a candidate path combination set C p in the middle; S4. selecting a path combination containing two paths from the candidate path combination set C p If a spectrum block satisfying the required number of frequency slots for the service transmission on the selected path can be found in the candidate path combination containing only two paths, the two-path transmission strategy is adopted to transmit the service; otherwise, the service is divided into smaller sub-services and the three-path transmission strategy is adopted to transmit the service. S5, according to the path fragmentation rate formula, the path fragmentation rate of each core on each path in the selected path combination is calculated, and the core in the path is selected through the path fragmentation perception strategy; on each path in the selected candidate path combination, a spectrum allocation strategy based on spectrum and crosstalk perception is used to allocate the spectrum block with the minimum difference from the required spectrum block of the service and less than the crosstalk threshold to the service.

2. The survivable multipath resource allocation method of claim 1, wherein: In step S3, if the number of paths in the shortest path set P is greater than or equal to 3, the first three paths in P are combined two by two to obtain P n , n = 1, 2, 3, and stored in the candidate path combination set C n in ascending order of the total length of the paths. p = {P1, P2, P3, P4}, where P4 represents a combination of three paths in P. If there are only two paths in the shortest path set P, then the combination of the two paths is stored in the candidate path combination set C p = {P1}.

3. The survivable multipath resource allocation method of claim 1, wherein: Step S4 comprises the following steps: S41, judging the candidate path combination set C p whether C is empty; if C is not empty, go to step S42; if C is empty, block the service request; p not empty, go to step S42; if C is empty, block the service request; p empty, block the service request; S42, if all the two-path combination transmissions in the candidate path combination set C p If all the two-path combination transmissions in the candidate path combination set C fail, the three-path combination P4 is used to transmit the service, and step S44 is entered. Otherwise, the candidate path combination P is selected from the set C in turn p n Wherein n = 1, 2, 3, the two-path combination transmission strategy is adopted for service transmission, and step S43 is entered.​ S43, according to the required transmission rate of the service and the protection ratio, calculate the required number of frequency slots of the service on each path when transmitted on the combination of two paths; if the maximum idle frequency spectrum block on each path in the selected path combination satisfies the required number of frequency slots of the service transmitted on the path, execute the core selection strategy, enter step S5; otherwise, delete the path combination from the set C p and return to step S41; S44, selecting candidate path combination P4 from set C p S44, selecting candidate path combination P4 from set C p S44, selecting candidate path combination P4 from set C p S44, selecting candidate path combination P4 from set C p S44, selecting candidate path combination P4 from set C p S44, selecting candidate path combination P4 from set C p S44, selecting candidate path combination P4 from set C p S44, selecting candidate path combination P4 from set C p S44, selecting candidate path combination P4 from set C p S44, selecting candidate path combination P4 from set C p S44, selecting candidate path combination P4 from set C p S44, selecting candidate path 4. The survivable multipath resource allocation method of claim 3, wherein: In step S43, when the service is transmitted by using two path combinations, the number of required frequency slots on each path is: wherein R i denotes the i-th service request; denotes when the service request R i the number of frequency slots required on each path; B denotes the service transmission rate in Gbps; q x B denotes the service transmission rate under the condition that the service protection ratio q is satisfied; B fs denotes the bandwidth provided by a unit frequency slot; M i denotes the modulation format level of the service request R i ; GB represents the number of protection frequency slots.

5. The survivable multipath resource allocation method of claim 3, wherein: In step S44, when the service is transmitted on the first two paths of the candidate path combination P4, the number of required frequency slots is: When the service is transmitted on the third path of the candidate path combination P4, the number of required frequency slots is: where R i represents the ith service request; represents the number of frequency slots required when the service request R i represents the number of frequency slots required when transmitted on the first two paths of the candidate path combination P4; represents the number of frequency slots required when the service request R i represents the number of frequency slots required when transmitted on the third path of the candidate path combination P4; B represents the service transmission rate in Gbps; q x B represents the service transmission rate under the condition of satisfying the service protection ratio q; B fs represents the bandwidth provided by a unit frequency slot; M i represents the modulation format level of the service request R i ; and GB represents the number of protection frequency slots.

6. The survivable multipath resource allocation method of claim 1, wherein: Step S5 comprises the following steps: S51, according to the graph vertex coloring theory, the non-adjacent cores in each path are grouped in turn, and are divided into a high-priority core group, a secondary-priority core group and a low-priority core group, and the core quantity ratio corresponding to the three core groups is 3:3:1; S52、According to the path fragmentation rate formula, the path fragmentation rates of the high-priority core group, the secondary-priority core group and the low-priority core group on each path in the selected path combination are calculated in turn, and each core group in the path is arranged in descending order of the path fragmentation rate and stored in the candidate core set C sort In the middle; S53, judging the set C sort whether empty; if empty, return to step S4; if not empty, select the core with the largest path fragment ratio S54, store all available spectrum blocks in the selected core into a set FB of available spectrum blocks available , and arrange the available spectrum blocks in the set FB available in non-decreasing order of the number of frequency slots; the available spectrum blocks represent spectrum blocks that satisfy the required number of frequency slots for service transmission in the path. S55, judging the set FB available whether empty; if empty, selecting the first spectral block from the set FB sort deleting the selected core and returning to step S53; if not empty, selecting the first spectral block from the set FB available and proceeding to step S56; S56, calculate the inter-core crosstalk value XT generated by allocating the service to the selected spectrum block; if the inter-core crosstalk value XT is less than the inter-core crosstalk threshold value XT th , then allocate the selected spectrum block to the service; otherwise, delete the selected spectrum block from the set FB available , and return to step S55.

7. The survivable multipath resource allocation method of claim 6, wherein: In step S52, the path fragmentation rate formula is specifically: In the formula, Θ c denotes the path fragmentation rate on the fiber core c; FB i denotes the number of frequency slots contained in the i-th idle frequency spectrum block in the path; denotes the number of i-th available idle frequency spectrum blocks in the path.

8. The survivable multipath resource allocation method of claim 6, wherein: In step S56, the inter-core crosstalk value calculation method is: In the formula, n represents the number of adjacent cores of the selected core; L represents the core length of the service transmission; h represents the average increase of crosstalk per unit length in the core: where ε represents a coupling coefficient, r represents a bending radius, β represents a propagation constant, ω tr represents a core pitch.

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