Communications method between a main station and processing nodes includes interconnecting the main station and the nodes in an optical path defining adjacent nodes and non-adjacent nodes, operatively grouping the nodes in a plurality of distinct sub-groups, each formed by non-adjacent nodes, at least one of said sub-groups including at least two nodes generating at the main station a multiplexed optical signal propagating along the path for serving the nodes, the multiplexed optical signal including a plurality of optical channel signals having a respective plurality of distinct carrier wavelengths, each carrier wavelength being associated with a respective sub-group of nodes, and serving each node of each sub-group of nodes with a respective portion of the optical channel signal having the associated carrier wavelength.