Crosstalk and interconnection distance considerations for board-to-board optical interconnects using 2-D VCSEL and microlens array

We describe the design and experimental characterization of a substrate-mode optical backplane using 0.5-, 0.75- and 1-mm spacing two-dimensional (2-D) optical beam arrays. The system uses arrays of multiplexed holograms to implement free space board-to-board interconnects, and employs 250-μm pitch 2-D vertical-cavity surface-emitting lasers (VCSEL) and microlens array as a transmitter to provide 0.5- to 1-mm spacing 2-D beam array, operating at 850 nm. By comparing the optical beam properties at the detector plane including the spot size and power uniformity of the optical beam array, as well as signal-to-noise ratio (SNR), the maximum interconnect distances are justified. Furthermore, we point out the improvement of the throughput that can be achieved by 2D crosstalk analysis within the same design concept. The results of crosstalk analysis obtained here can be used for application to the standard five-board free-space optical backplane system.