To clarify the requirements as regards the geometry of multicore fiber, we examined its minimum cladding thickness and maximum cladding diameter experimentally. We studied the relationship between cladding thickness and transmission loss for an eccentric core structure and revealed that the cladding thickness is mainly limited by confinement loss. We also confirmed that the dynamic fatigue corrosion of the optical fiber exhibits no clear dependence on coating thickness or cladding diameter. We discussed the relationship between the effective core area and the core multiplicity factor by considering several arrangements. We showed that optimizing the relationship between core arrangement and effective core area can maximize the core multiplicity factor.