The graphic representation of a switching network can play an important role in a switching system design. Among various representations, bipartite graphs are particularly powerful. Several attributes of a bipartite graph can be exploited in designing switching systems. First, in a network based on bipartite graphs, no two paths are allowed to intersect at a vertex. This attribute is exploited in this paper to design a directional coupler-based photonic switching network with very low crosstalk. Since at the present time, crosstalk is the most limiting factor in constructing a large directional-coupler-based photonic switching network, how to reduce crosstalk on the device and architecture levels is an important design issue. Second, broadcast is an intrinsic property of a bipartite graph (the same is not always true with a crossbar representation), and it can be exploited in designing multiconnection switching networks. Third, bipartite graphs have a nonplanar nature which make them well suited for three-dimension free-space-transmission photonic switching systems. Finally, a new class of switching networks, also based on bipartite graphs, is proposed. They have many interesting characteristics: O (log2 N) stages between each inlet-output pair, simple path hunt, self-routing capabilities, etc. These characteristics can be used in designing high-speed electronic and photonic switching systems. © 1990 IEEE
