In an automatically switched optical network operating according to a wavelength plan, the wavelengths are assigned to an optical path based on availability, performance and SRS wavelength coupling reduction. First, the wavelengths are grouped in static bins based on their reach versus cost performance, and each bin assumes a ΔQ of a middle wavelength. Then, the bins are moved into subsets of dynamic bins, constructed using bin constraints that account for the particulars of the respective optical path. The path is characterized taking into account the wavelength currently accessing at the end nodes, and the wavelength tandeming through the end nodes. Wavelength selection starts with the bins that satisfy the maximum number of constraints, and the wavelengths are checked sequentially against wavelength constraints; relaxed constraints are also applied when it is not possible to exactly satisfy one or more constraints.