In recent many-core architectures, the number of cores has been steadily increasing and thus the network latency between cores becomes an important issue for parallel application programs. Because packet-switched network structures are widely used for core-to-core communications, a topology among cores has a major impact on the network latency. It has been reported that a small-world Network-on-Chip that adds links between randomly-selected routers on a regular router topology is effective for reducing the network latency. In this study, we extend this framework by connecting multiple links between a single core and quasi-optimally selected neighboring routers to form multiple links from each core on a 2D MESH router topology. Results obtained by a flit-level discrete event simulator show that our optimized core-link topologies can achieve the average latency up to 48% lower than that of baseline topologies. Furthermore, full-system CMP simulation results show that by using optimized core-links we can improve the application execution time on the NAS Parallel Benchmarks by up to 10.1%.