摘要： This paper reviews the characteristics of coupled and uncoupled multicore fibers for enhancing the capacity of optical fiber communication system by utilizing both the space and mode division multiplexing technologies. Various limitations in realizing efficient few mode multicore fiber (FM-MCF) design are analyzed in this paper. For both types of fibers, achievable spatial channel count, crosstalk and dispersion behavior, nonlinear effects and overhead at the receiver side are discussed. Some of the reported coupled MCF and uncoupled MCF designs are also summarized from the view point of mechanical reliability and transmission characteristics of the fiber. The constraints of the state of the art fiber designs are discussed. Also the advantages and drawbacks of both types of the fibers were reviewed. It has been observed from the existing MCF designs that, improvement in one transmission characteristics costs the other required characteristics to degrade. Finally it is outlined in this paper that, in order to make the space and mode division multiplexing more efficient and realistic in all aspects simultaneously, still better optimization in the MCF system design is required and the same can be achieved with the development of novel FM-MCF fibers, active and passive devices, data modulation techniques and signal processing algorithms.