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In this paper, we address the problem of the strictsense nonblocking operation of an elastic optical switch. Elastic optical switches are used as nodes in elastic optical networks (EONs), where fine granular frequency slots or flexible grids are used in opposite to the traditional optical networks, where fixed grids are used. The switch architecture considered in this paper consists of waveband converting switches in input and output stages, while in the center stage there is only one wavelength selective space switch without wavelength conversion capabilities. We derive the number of frequency channels k needed in interstage links to ensure the nonblocking operation of the switch when input and output links have n frequency channels and a frequency slot of one connection is not greater than m frequency channels. Both, necessity and sufficient conditions are proved.

This paper considers the three-stage switching fabrics of the wavelength-space-wavelength architecture, called the WSW1 switching fabrics, for elastic optical nodes. Seven control algorithms for simultaneous connection routing are described. One algorithm is designed for the WSW1 switching fabric with two inputs and two outputs, four algorithms for the WSW1 switching fabric with three inputs and outputs, and two algorithms for nodes with a capacity greater than 3. We establish the necessary conditions for rearrangeability and prove sufficient rearrangeable conditions for the proposed algorithms. In cases where the switching fabric capacity is a multiple of 3, the sufficient conditions obtained for the proposed algorithms are the best known and close to the necessary conditions. INDEX TERMS Elastic optical networks, optical switches, rearrangeable switching fabrics, control algorithms.

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