In this paper, we show numerical simulations for analyzing spatially multiplexed systems based on orthogonal frequency division multiplexing and multiple-input multiple-output Alamouti code in order to compare the performance of the transmission in a two-core fiber with low coupling, and in few-mode fiber with high differential group delay. These new fibers are the most recent alternatives used for improving the throughput of long-haul and high-speed optical fiber networks. We compare the bit-error-rate of two orthogonal frequency division multiplexing signals, after 100 km of optical fiber, considering only its linear effects. The first one uses an 8 phase-shift keying signal operating at 130 Gbps, and the second one uses a 16 quadrature amplitude modulated signal operating at 170 Gbps. Our results show a better bit error rate performance using a few-mode fiber, compared with a two-core fiber. Additionally, Alamouti code shows a better effectiveness for compensation of linear impairments in a two-core fiber in comparison with a few-mode fiber.