Determination of minimum number of wavelengths required for all-optical WDM networks using graph colouring

The minimum number of carrier wavelengths required for full interconnection of a wavelength-routed optical fibre network was determined using the graph colouring of a `shortest-path graph´. derived from the original network description. No two messages with the same carrier wavelength and different source/destination pass over the same communication link, and all sources connect to all possible destinations. The results are applicable to a national wavelength-division multiplexed back-bone network