Free space optical multicast crossbar

Enabling multicast in optical networks requires the use of multicast-capable optical switches. In this paper, we propose a new class of multicast-capable free space optical (FSO) switches. Our design exploits nonmovable tri-state switching elements (T-SEs) that support signal splitting and switching simultaneously and seamlessly, and thus the separate splitting stages used in 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 only through the crossbar. The proposed FSO switch is analyzed and compared to conventional architectures in terms of hardware complexity, power loss, and cost. We show that an N x M switch requires only NM nonmovable T-SEs. Comparison with existing optical multicast switches shows that the proposed switch provides multicast capability with substantially lower hardware complexity and a comparable performance. Cost analysis for the proposed switch shows that its switching cost is lower than existing switches even if the cost of the T-SE is 1.2 to 2.2x that of a MEMS mirror.