Communication technologies are challenged by a global demand for data traffic that grows exponentially, fueled by more and more bandwidth-hungry applications that rely on the internet. Space-division multiplexing (SDM) on few-mode fibers (FMFs) and multi-core fibers (MCFs) is a revolutionary approach that has been considered in recent years to prevent the capacity crunch of the optical transport network – the back-bone of the global telecom infrastructure – and many lab demonstrations of SDM have been on the spotlight of the major conferences in the field. This proposal has the ambition of demonstrating the first deployed SDM system, bringing SDM from lab experiments to field trials. This revolutionary transition is enabled by a synergy with project INCIPICT, which makes available to FIRST a pioneer SDM fiber-optic infrastructure. By gathering together the most prominent Italian research groups in the area of optical communications, FIRST targets demonstrating the effectiveness and viability of SDM in FMFs and MCFs, as well as its superior performance in the comparison with standard single-mode fiber technology that is used today. The results of FIRST will provide the ultimate demonstration of SDM transmission, well out of reach of lab experiments relying on spooled fibers.