| Demand for large transmission capacity drives the research of high-capacity optical transmission systems. Multi-core fibers (MCFs) applied in space division multiplexing (SDM) transmission systems have been intensively investigated so far. In this paper, hole-assisted multi-core optical fibers are investigated systematically by coupled mode theory and coupled power theory. Hole-assisted six-core fibers with ring core and linear core configurations are involved. For homogeneous structure of six-core optical fiber, the non-adjacent cores coupling coefficients and self-coupling coefficients are taken into account in theoretical analysis. For hole-assisted multi-core fibers, air hole radius, the distance between the core and air hole, the core-to-core distance are important parameters which could influence the coupling coefficients, crosstalk and mode area. It is shown that coupling coefficient can be reduced by increasing the core-to-core distance and air-hole radius, or decreasing the distance between the core and air-hole. Crosstalk can be reduced by increasing the core-to-core distance, the air-hole radius or the distance between the core and air-hole. Mode area can be instance by increasing the core radius and decreasing the distance between cores, the air-hole radius and the distance between the core and air-hole. Specifically, with125μm fiber cladding diameter, the mode area of each core for ring hole-assisted six-core fiber could reach120-150μm2, meanwhile maintaining low crosstalk (-30dB or less). The conclusions are of significance for designing and manufacturing of hole-assisted multi-core fibers. |
