Low-distortion hybrid optical shuffle concept.

A hybrid micro-macro-optical shuffle interconnection approach is described. The new concept minimizes distortion in multichip smart-pixel shuffle interconnection systems that use macro-optics to link dense arrays of vertical-cavity surface-emitting laser (VCSEL) sources and matching arrays of detectors. The typical narrow-beam cones of VCSEL's are exploited by use of beam-deflecting micro-optics to create an optical system that is symmetric about its aperture. Since symmetric systems are well known to cancel distortion, this novel concept provides the means to achieve the required high degree of interchip registration accuracy.

Multichip free-space global optical interconnection demonstration with integrated arrays of vertical-cavity surface-emitting lasers and photodetectors.

The experimental optical interconnection module of the Free-Space Accelerator for Switching Terabit Networks (FAST-Net) project is described and characterized. Four two-dimensional (2-D) arrays of monolithically integrated vertical-cavity surface-emitting lasers (VCSEL's) and photodetectors (PD's) were designed, fabricated, and incorporated into a folded optical system that links a 10 cm x 10 cm multichip smart pixel plane to itself in a global point-to-point pattern. The optical system effects a fully connected network in which each chip is connected to all others with a multichannel bidirectional data path. VCSEL's and detectors are arranged in clusters on the chips with an interelement spacing of 140 microm. Calculations based on measurements of resolution and registration tolerances showed that the square 50-microm detector in a typical interchip link captures approximately 85% of incident light from its associated VCSEL. The measured optical transmission efficiency was 38%, with the losses primarily due to reflections at the surfaces of the multielement lenses, which were not antireflection coated for the VCSEL wavelength. The overall efficiency for this demonstration is therefore 32%. With the measured optical confinement, an optical system that is optimized for transmission at the VCSEL wavelength will achieve an overall efficiency of greater than 80%. These results suggest that, as high-density VCSEL-based smart pixel technology matures, the FAST-Net optical interconnection concept will provide a low-loss, compact, global interconnection approach for high bisection-bandwidth multiprocessor applications in switching, signal processing, and image processing.