A method for dynamic routing an optical signal in an optical network is provided, including: executing a shortest-path algorithm receiving input concerning a source node, a destination node and the topology of the network, providing a shortest-path tree comprising nodes and arcs connecting the nodes, the shortest-path tree comprising branches along which an effective attenuation is no greater than a predetermined limit, each branch comprising an end node and each end node being associated with a corresponding set of wavelengths; checking, for each end node having no wavelength conversion resources and for each wavelength, if the end node is connected to at least another node external to the branch through the wavelength; excluding, for any end node if the result of the checking is negative for at least one wavelength, the at least one wavelength from the corresponding set of wavelengths, thus updating the topology; and re-executing the shortest-path algorithm.