multicore optical fibers that include between two and ten multimode cores surrounded by a cladding matrix and symmetrically arranged about a fiber axis are disclosed , with no core running along the fiber axis . the cores include a trench to stabilize delays of the higher order modes , which tend to propagate faster than do the central modes due to the amount of power at the core - clad interface . the trench also suppresses crosstalk and power leakage . the core configuration promotes efficient optical alignment and optical coupling with other multicore optical fibers or light sources , such as vscel and silicon - photonics light sources .