Optical link for an adaptive, redundant, misalignment tolerant, free-space optical interconnect system at 1.25Gbs

Free-space optical links can provide high bandwidth, flexible, high-density interconnections between electronic elements within computers and switches. These links function with no physical contact but suffer from poor tolerances to misalignment. This thesis presents the design and implementation of an optical link which exploits the spatial redundancy between arrays of active optoelectronic elements in order to obtain a high misalignment tolerance between them. The system consists of four optical links operating between two printed circuit boards. Each optical link pair constitutes a bi-directional channel. Each of the links is designed to function at 1.25Gb/s, yielding an aggregate bandwidth of 5Gb/s for the system. The system is design to function under +/-1 mm and +/-1° of lateral and angular misalignments, respectively, with a working distance between the boards varying from 5 cm to 22 cm. The design of the system makes it ideal for rack or shelf based optical interconnections.The design of this optical link exploits the spatial redundancy between a two-dimensional array of vertical cavity surface emitting lasers (VCSEL) and a two-dimensional array of photodetectors (PD). The link makes use of a refractive microlens array as a collimating optic, and of bulk achromatic lenses for both collimation and focusing of the beams at each end of the optical link. This thesis presents the optomechanical packaging, optoelectronic packaging and precision alignment of the active and passive elements of the optical link. Experimental results for the link, showing misalignment tolerances greater than +/-1.25mm laterally and +/-1° angularly are presented