Lightpath (wavelength) routing in large WDM networks

We address the problem of efficient circuit switching in wide area optical networks, The solution provided is based on finding optimal routes for lightpaths and the new concept of semilightpaths. A lightpath is a fully optical transmission path, while a semilightpath is a transmission path constructed by chaining together several lightpaths, using wavelength conversion at their junctions, A fast and practical algorithm is presented to optimally route lightpaths and semilightpaths taking into account both the cost of using the wavelengths on links and the cost of wavelength conversion, We prove that the running time of the algorithm is the best possible in the wide class of algorithms allowing linear algebraic operations on weights, This class encompasses all known related practical methods. Additionally, our method works for any physical realization of wavelength conversion, independently whether it is done via opto-electronic conversion or in a fully optical way.