A method implemented by a processing device for gridless optical routing and spectrum assignment on links in an optical network includes, responsive to one or more new channel requests, performing a path computation utilizing frequency markers to determine feasibility of the one or more new channel requests, wherein the optical spectrum is represented as a real line with the frequency markers indicative of used optical spectrum; allocating the one or more new channel requests based on the path computation and allocation criteria; and responsive to allocating the one or more new channel requests, updating the associated frequency markers on the real line.