Thermo-optical numerical modal analysis of multicore fibers for high power lasers and amplifiers

•Multi-core fibers show high robustness to stressors such as heat load.•Heat load breaks the degeneracy of the cores’ FMs, reducing core coupling.•This allows smaller pitch and higher number of cores per unit area.•Fiber bending does not significantly alter coupling and effective area of MCFs.•Bending reduces higher-order mode core overlap, enhancing effective monomodality.•Numerical results show effective monomodality with core effective area of 181 μm2.•Minimum pitch is 35 μm for straight and bent fibers with total area of 85 x 85 μm2.