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.

In this paper, we consider the necessary and sufficient rearrangeability conditions for the wavelength-space-wavelength switching fabric, called the WSW2 switching fabric, for elastic optical network nodes. We derive and prove the lower bound of the necessary conditions for such switching fabrics to be rearrangeable. We also show the upper bound of the sufficient conditions for the rearrangeability of the switching fabric with two input and two output switches. For simultaneous connection routing, we propose a routing algorithm that always ends with success in switching fabrics, which fulfill the sufficient conditions. Finally, we extend the proposed algorithm to the switching fabric with r input and r output switches, and we derive the conditions under which this routing algorithm always ends in success. The required number of center-stage switches is significantly lower than that in the strict-sense nonblocking switching fabrics. To our knowledge, the proposed routing algorithm is the first one which ends with success for any connection set, within the provided sufficient conditions. INDEX TERMS Elastic optical network, optical switch, rearrangeable switching network, simultaneous connection routing algorithm.