Minimization of Wavelength Conversions

In multihop WDM networks where wavelength converters are equipped at some routing nodes, a connection between two communication nodes consists of one or more lightpaths. A wavelength conversion is required at the joint of two lightpaths if they use different wavelengths. Wavelength conversion can be done either electronically or optically. In electronic approach, optic-electronic-optic conversion is required and it causes long delay compared with the transmission of light signals. In all optical approach, the optical signal is allowed in the optical domain throughout the conversion process, however shifting wavelength channels from one to another makes routing/switching complicated. Therefore, in either case, it is desirable to minimize the number of wavelength conversions used to reduce the conversion delay and workload of routing nodes.