Minimizing drop cost for SONET/WDM networks with wavelength requirements

SONET/WDM networks using wavelength add–drop multiplexing can be constructed using certain graph decompositions used to form a “grooming,” consisting of unions of certain primitive rings. The existence of such decompositions when every pair of sites employs no more than 8 of the wavelength capacity is determined, with few possible exceptions, when the ring size is a multiple of four. The techniques developed rely heavily on tools from combinatorial design theory. © 2001 John Wiley & Sons, Inc.