Space-division multiplexing (SDM) has been proposed to increase fiber transmission capacity to cope with the increasing bandwidth requirements in the network. The use of multicore fiber (MCF) is considered to be a simple and feasible way to implement SDM technology. The intercore crosstalk (XT) in the MCF affects the performance of network transmission. Currently, bidirectional transmission of MCF has been proven to have lower XT than traditional unidirectional transmission of MCF. But there are few research studies on routing, core, and spectrum allocation strategies with bidirectional transmission. Thus, to get more XT reduction, we propose two different routing, core, and spectrum allocation strategies according to the traffic loads in the network based on the bidirectional transmission of MCF. The simulation results show that the proposed algorithm has lower blocking rate and higher resource utilization than the benchmark algorithm in the two stages of different traffic loads in the network.