## 1 Introduction
To reduce crosstalk, high-order modulation can be used to increase the transmission rate of services, but it will limit the allocation and use of frequency slot resources, thereby increasing the blocking ratio. In order to reduce the blocking ratio, it may increase the crosstalk ratio between cores, and high-order modulation cannot be used, thereby affecting the transmission rate of the service. Therefore, our algorithm comprehensively considers the blocking ratio and crosstalk ratio. We use a multi-objective method to balance the relationship between the two to obtain better solutions. Ref. [12] established a multiobjective model and designed a corresponding multiobjective optimization algorithm to solve it. However, it does not consider core switching. In this paper, we focus on solving the static RSCA problem that considers inter-core crosstalk and core switching in MCF-EONs. Our work makes three key contributions: (a) we consider simultaneously core switching and multiple optimization objectives, i.e., the static RSCA based on core switching (RSCA-CS) problem is formulated as a true multiobjective ILP model, which minimizes both the network requests blocking ratio and crosstalk ratio; (b) in contrast to previous works [9; 10; 11; 12] that separately code the routing and core into two populations resulting in a time-consuming solution. We design a novel joint routing and core coding scheme under core switching for the first time. A single chromosome accurately expresses a solution to this complex problem in our work. The solution space encoded in this way is discrete and is beneficial to the global convergence of solutions; (c) a new adaptive hybrid multiobjective optimization algorithm with several key mechanisms designed especially is proposed to solve such a model efficiently on the basis of the novel joint routing and core coding scheme. To enable the algorithm to search uniformly in the objective space during the initial iteration and to evolve on the basis of a better solution set, we design a hybrid algorithm combining uniform design method and heuristic algorithm without core switching for simplification. Single-point crossover, hybrid mutation, and adaptive mechanisms will help the algorithm achieve a better balance between global exploitation and local exploration. The algorithm integrates multiple strategies into a multiobjective evolutionary algorithm based on the decomposition (MOEA/D) framework, which solves the problem from the perspective of multiple objectives and can provide network operators with multiple resource allocation schemes whose objective values are diversionary and not dominant, allowing the resource allocation to better meet the diversified goals of both operators and users. The rest of this paper is organized as follows. Section 2 is related work. Section 3 introduces some prerequisite knowledge, including spectrum allocation in optical WDM networks versus EONs, MCF, MCF-EON architecture, core switching, and inter-core crosstalk. Section 4 describes the RSCA-CS problem and formulates it as an ILP mathematical model. Section 5 introduces the proposed key elements and mechanisms of our novel algorithm in detail. Simulation experiments and result analysis are addressed in Section 6. A conclusion is finally drawn.