Embodiments provide an optical transmission system comprising an optical transmitter configured to transmit data over an optical fiber transmission channel comprising a multi-core fiber, the data being carried by one or more optical signals propagating along the multi-core fiber according to a plurality of cores, each core among the plurality of cores being associated with one or more core parameters, wherein the optical transmission system comprises a core selection device configured to select a set of transmit cores among the plurality of cores according to a transmit core selection criterion, the transmit core selection criterion being related to the one or more core parameters, the optical transmitter being configured to transmit the data over the set of transmit cores.