“…More "conventional" MOF configuration is based on stacks with inclusion of doped silica rods. According to published results of simulations and theoretical researches, increased refractive index of MOF cores improves unique properties characteristic of all-silica multi-core MOFs (in-phase supermode regime [36][37][38][39] ; band pass filtration and splitting 40,41 ) and discovers novel features (guiding systems for optical networks with using SDM technique 42,43 ; SDM channel multiplexing / demultiplexing [44][45][46][47] ). There is a set of published works [48][49][50][51][52][53][54] , concerned with Yb-doped multicore (6 48,50,51 , 7 52,54 , 12 49 , and 18 53 cores) MOFs/PCFs for high power fiber lasers, while GeO2-doped core MOFs was designed and fabricated for supercontinuum generation (3 cores) 55,56 , and for guiding systems 57 and splitters 58 for SDM fiber optic transmission system / next generation optical networks (7 cores).…”