Asymmetrical Space-Conversion-Space SCS1 Strict-Sense and Wide-Sense Nonblocking Switching Fabrics for Continuous Multislot Connections

Recently, Danilewicz et al. have proposed two strict-sense nonblocking structures of switching fabrics, called Space-Wavelength-Space 1 and Space-Wavelength-Space 2, for elastic optical network nodes. This paper considers one of the two previously presented structures. The node uses a three-stage switching fabric that applies space switching in the first and third stages and wavelength switching in the second stage (an S-W-S switching fabric). In elastic optical networks, an optical path can use a frequency slot spread over m adjacent frequency slot units. Such a connection is called an m-slot connection. In this paper, a more general case is presented in which conversion in the middle-stage switches can be made for one of the different domains (frequency, time, etc.). However, the m-slot connections are a basis for the presented theory. This theory concerns space-conversion-space (S-C-S) switching fabrics in which conversion can be performed for different domains. Danilewicz et al. considered S-W-S switching fabrics in which 1 ≤ m ≤ m
_max
. For the S-C-S switching fabrics discussed in this paper, we derive and prove strict-sense nonblocking conditions when m-slot connections are set up, in which m
_min
≤ m ≤ m
_max
. Strict-sense nonblocking conditions are derived for asymmetrical S-C-S switching fabrics. In addition, wide-sense nonblocking conditions for switching fabrics with functional decomposition of center-stage switches are presented. It is shown that the wide-sense nonblocking switching fabrics may require less than a half of the switches in the middle-stage compared with the strict-sense nonblocking switching fabrics.