DESIGN LIMITATIONS OF HIGHLY PARALLEL FREE-SPACE OPTICAL INTERCONNECTS BASED ON ARRAYS OF VERTICAL-CAVITY SURFACE-EMITTING LASER-DIODES, MICROLENSES, AND PHOTODETECTORS

We utilize a novel diffraction formalism to study the crosstalk effect in a highly parallel free-space optical interconnect based on two-dim ensional arrays of surface-emitting laser diodes, microlenses, and pho todetectors. The diffraction induced crosstalk between adjacent laser diodes in each detector to the system limitations is investigated. Opt imum design rules and formulas are given for the first time, to includ e the relation of channel packaging density and interconnect length to the design parameters of the optical interconnect components. The des ign formulas developed here yield an optimum detector size and indicat e a tradeoff between channel packaging density and interconnect length . The feasibility of such a free space interconnect with a channel pac kaging density of 3460 channels/cm(2) and 2.0 cm interconnection lengt h is determined using typical parameters of detector radius from simil ar to 5 to similar to 45 mu m, lens radius of 85 mu m, and laser diode radius of similar to 5 mu m operating at wavelength 0.67 mu m for sig nal-to-noise ratio above 12 dB. Some experiments were conducted to mea sure the diffraction induced crosstalk and optical link efficiency.