An optical transmission system comprising an optical transmitter configured to transmit data over an optical fiber transmission channel comprising a multi-core fiber, said data being carried by optical signals, said optical signals propagating along the multi-core fiber according to two or more cores, said multi-core fiber being associated with fiber parameters and misalignment losses values, at least one scrambling device being arranged in said optical fiber transmission channel for scrambling said two or more cores according to a scrambling function, wherein the optical fiber transmission channel comprises a system configuration device configured to determine a core dependent loss value depending on the fiber parameters, at least one misalignment loss value, a number of said at least one scrambling device, and the scrambling function.