Alignment considerations in packaging array-based optical interconnects and processors

Because of micron-level size of optical components in arrays used in high-speed optical interconnection or switching systems, and the large number of elements in such arrays, achieving the alignment necessary for the optical interconnect to operate correctly and reliably is a difficult task. A tool for quantitatively specifying the relative difficulty of aligning the arrays of optical components in an optical package is developed in this paper. The alignment of two rigid arrays, one of optical sources and the other of optical receptors is analyzed. The power coupling efficiency between the source and the receptor array elements is determined based on their sizes, inter-element spacing and distances, and the six possible types of random offsets that can occur owing to the positioning of the arrays. The cross-talk level is calculated. A statistical measure of the ease or difficulty with which an optical interconnect can be aligned is then determined. This measure, called the array-alignability, uses the probability of achieving a given efficiency of power transfer in spite of the random offsets. Since efficiency varies with changing component sizes, positioning tolerances, etc., the array-alignability depends upon various size and shape parameters. An optical interconnect or switching processor in which array-alignability is high has an easier task of alignment and is more tolerant of various offsets.