## 1 Introduction  
With the rapid progress of information technology, many Internet services and applications have been developing widely, resulting in an explosive increase in network traffic. However, the existing optical wavelength-division multiplexing (WDM) networks with fixed spectrum grid and modulation format that lead to low spectrum utilization in optical fiber links are failing to meet the growing and diversified traffic demands of the future. Therefore, it is urgent to develop a new high-capacity network with variable grids and scalable architecture. Elastic optical networks (EONs) based on orthogonal frequency division multiplexing (OFDM) technology, first proposed in 2008, use the narrow frequency slot (FS) as a unit of resource allocation, which makes it feasible for EONs to dynamically allocate spectrum resources and configure modulation formats according to user demands and traffic volume [1]. However, with the ever-growing expansion of the current optical communication network coverage and the rapid growth of service requirements, the physical capacity of single-mode fiber (SMF) will approach its channel Shannon limit soon. Therefore, it is necessary to develop new optical fiber technologies, among which, space division multiplexing (SDM) technology that uses the space dimension to significantly increase transmission system capacity, is a promising solution [2]. As one of the most easily implemented technologies in SDM with an obvious network expansion effect, multi-core fiber (MCF) aggregates multiple single-mode cores into fiber cladding to realize exponential growth in capacity over single-core fiber. MCF has found some applications in the centers [3] and submarine scenarios [4]. Therefore, EONs with multi-core fiber (MCF-EONs) have attracted extensive attention from researchers since their appearance, and their resource allocation has been a hotspot in recent years and remains more challenging than that of EONs. Due to the increasing core dimension, the corresponding routing, spectrum and core assignment (RSCA) problem is more complicated and challenging, and we need to reconsider more constraints compared with EONs. Therefore, new algorithms should be used to solve this problem instead of directly employing the existing algorithms for tackling a routing and spectrum assignment (RSA) problem in EONs. In addition, crosstalk will occur when the RSA algorithm distributes connection requests on the same FSs between adjacent cores. Accordingly, inter-core crosstalk needs to be considered in solving this problem. To expand the routing space and further utilize the limited EON resources, cores on different links can be freely switched, i.e., core switching can be realized at each node of a network. Thus, it is significantly important to study the resource allocation problem and its solving algorithm when considering core switching and inter-core crosstalk for obtaining better MCF-EONs performance. Through the above analysis, we find that some recent studies have some defects. However, Ref. [2] did not consider inter-core crosstalk. Refs. [5; 6; 7] considered inter-core crosstalk but did not consider core switching. Ref. [8] studied the RSCA problem by considering both inter-core crosstalk and core switching and proposed a heuristic algorithm, however, they did not use an intelligent algorithm. For the static RSCA problem [9; 10; 11; 12], used an intelligent algorithm, but there is no study that simultaneously considers core switching, constructs a true multiobjective optimization model, and designs corresponding multiobjective algorithms to tackle such a model. Therefore, we focus on considering the static RSCA problem that considers inter-core crosstalk and core switching in MCF-EONs, and use an intelligent algorithm to solve the problem. To sum up, the single-objective algorithm either aims to reduce the blocking ratio or to reduce the crosstalk ratio.