Compact design for MEMS cross-connect switches

A simple approach for designing large-scale mirror-rotation free-space optical cross-connect switches based on arrays of MEMS tilt mirrors is described. The layout of a compact switch is first presented. Using existing theory of Gaussian beams, the parameters of the beam that maximises the port count for a given mirror turn angle is then identified. This beam is the narrowest that can propagate over a fixed distance, and its maximum mode radius forms a limiting envelope to the variations in mode radius of all Gaussians. Because this beam has known and predictable parameters, it can be used as a yardstick to compare designs with different port number. The supporting optics needed to create this beam from a given fibre is defined.