In recent years, the rapid increase in network traffic requires more network transmission capacity. Therefore, an elastic optical network based on orthogonal frequency division multiplexing technology is proposed. Its characteristic is to allocate spectrum resources according to the connection requests. By improving the utilization efficiency of spectrum resources in the frequency domain, the network transmission capacity can be expanded. However, restricted by the Shannon limit, the traditional single-core single-mode fiber is difficult to further expand the transmission capacity in the network. Therefore, on the basis of the proposed multi-core optical fiber (MCF), space division multiplexing elastic optical networks (SDM-EONs) are considered as one of the most potential solutions to break through the network capacity bottleneck. At the same time, the applications in the network have diversified demand characteristics, but it is difficult for physical facility providers to flexibly configure the network according to the specific needs of the applications. In recent years, the increasingly developed network virtualization technology has solved the problem of network rigidity and formed a diversified network structure. The combination of network virtualization technology and SDM-EONs can improve the utilization rate of the underlying physical resources, but it will make the virtual network mapping more complex. Furthermore, virtual network mapping inevitably needs to meet more constraints. There are also physical layer constraints of inter-core crosstalk (XT) in SDM-EONs. When the overlapping spectral segments of adjacent cores are occupied by different optical paths at the same time, the transmission quality of optical paths will be degraded, and high-quality transmission of normal signals cannot be realized. Therefore, this paper focuses on SDM-EONs based on MCF to solve the virtual network mapping problem of crosstalk perception.

In this paper, the crosstalk impact of the occupied spectrum resources on the adjacent core spectrum is considered, and a crosstalk impact assessment method is designed. Then a virtual network mapping algorithm for crosstalk awareness (CA-VNM) in SDM-EONs is proposed. The virtual network mapping method adopted by the algorithm is two-stage mapping. The first stage is virtual node mapping. In order to enhance the correlation between virtual nodes and virtual links, virtual nodes adopt the virtual node proximity ranking method, and physical nodes adopt the node degree classification method, so as to improve the virtual network acceptance rate and provide the underlying physical resources for the subsequent virtual services with greater demand. The priority evaluation method of physical nodes considers the XT on the adjacent links of nodes to improve the utilization rate of the underlying physical resources and balance the XT. The second stage is virtual link mapping, and the virtual link bandwidth is prioritized. Based on the prioritization, the K-shortest path method is used to find the K optical paths with the least hops, and the physical link priority method is used to rank the candidate physical links. Then the core load balancing and spectrum partition allocation methods are designed to balance the traffic of each core and reduce the XT.

The algorithm proposed in this paper optimizes the network performance. The request acceptance rate of CA-CVM achieves the best effect in the comparison algorithms, and the highest request acceptance rate of the virtual network is increased by 11% (Fig. 6). CA-CVM obtains the best spectrum utilization performance in the NSFNET network, and the spectrum utilization is increased by 17.1% (Fig. 7). The XT improvement rate gradually decreases with the increase in the load because the idle resources in the network gradually decrease, and other methods cannot reduce the XT. The XT improvement rate of CA-CVM is the best. At 100, 200, 300, 400, 500, 600, 700, 800, and 900 Erlang, the XT improvement rates are 67.7%, 54.6%, 46.3%, 39.3%, 32.8%, 20.5%, 11.8%, 9.1%, and 7.0%, respectively (Fig. 8).

In this paper, a virtual network mapping algorithm for crosstalk awareness in SDM-EONs is proposed, and the constraints of virtual network mapping in SDM-EONs are considered. When the priority of virtual nodes is evaluated, the proximity between virtual nodes is considered, and a virtual node proximity ranking method is proposed. When candidate physical nodes are selected, the physical node degree is considered so that more underlying physical resources can be provided to the virtual request service with greater demand. A crosstalk impact assessment method is proposed to evaluate the weight of physical nodes and balance the crosstalk between cores. In addition, the core is selected according to the bandwidth required by the virtual link to balance the core load. Finally, the spectrum is divided into several regions, and the first hit and the last hit are used alternately when the spectrum is allocated to reduce the influence of XT. The simulation results show that when the network load is small, the acceptance rate of the virtual network is optimized by 11%, the spectrum utilization rate is increased by 17.1%, and the XT improvement rate can reach 67.7%. In view of this, the proposed algorithm can effectively improve the acceptance rate of the virtual network and the XT in the SDM-EONs and optimize the mapping performance of the virtual network.