New Class of Rearrangeable Nonblocking Multicast Free-Space Optical Switches

In this paper, we propose N x N rearrangeable nonblocking multicast free-space optical switches. Our design exploits nonmovable tri-state switching elements (TSEs) that support signal splitting and switching simultaneously and seamlessly, and thus, separate splitting stages used in the conventional multicast switches are not needed. It follows that the propagation loss that may be encountered by an optical beam passing through a splitting stage followed by a crossbar (e.g., splitter-and-delivery-based switches) can be avoided in the proposed switch, since the beam passes through only a single stage. The proposed switch exhibits an optimal hardware complexity, as it requires only N(N+1)/2 T-SEs. The switch is analyzed and compared to existing optical multicast switches in terms of hardware complexity, power loss, and cost. Comparison results show that the proposed switch provides multicast capability with a lower hardware complexity and a comparable performance. Cost analysis shows that for N = 4, the overall cost of the new design is lower than that of existing strictly nonblocking switches, even if the T-SE is 3.5 to 10 times the cost of typical microelectromechanical systems mirrors. In addition, we present a simple routing algorithm that systematically establishes connections over the new switch.