Design rules for highly parallel free-space optical interconnects

Abstract

Recently, a number of successful free-space chip-to-chip and board-to-board optical interconnects have been demonstrated. Here, we present some of the design rules that can be derived as a result of this work and also as a result of numerical and theoretical analyzes. We draw a number of conclusions. In the area of optoelectronic very large scale integration (VLSI) design, we suggest that differential electrical and optical transceiver designs provide the best performance. In the area of optical design, we present scaling and system partitioning laws for clustered optical relays and determine the interconnect distances at which microlens or macrolens systems are more suitable. We also show that the ease with which two modules can be aligned can be related to the optical invariant of the system and is, thus, a function of the size of the detector and the numerical aperture of the detector optics. Finally, we show that when multiple optical components must be aligned, very high individual component tolerances are required if the system as a whole is to have a high chance of success.

Realization of optical fibers terminated with ball lenses

“…This is reflected in a number of articles [1][2][3][4][5] and books related to the introduction of optical interconnectors for very-large-scale integration (VLSI) circuits [6][7][8][9]. A printed circuit board (PCB) makes use of optical systems communicating with each other in free space [10]. Such systems have the particular advantage of allowing for high density and -due to the use of, e.g., controllable micromirrors -for switching a light beam [11].…”

Power delivery, signaling and cooling for 2D and 3D integrated systems

“…However, such an approach limits the optical I/O density (because of fiber size and handling), increases the complexity of packaging, and potentially increases the cost of assembly because fibers must be manually (and serially) connected to each chip. High-density free-space optical interconnects are also being pursued for chip-to-chip communication [11,12,13]. However, susceptibility to misalignment and complexity in packaging are formidable challenges that have yet to be fully addressed.…”

Wavefront and polarization effects in actively tunable thin-film resonators for beam alignment in optical interconnects

“…Optical interconnects are a promising solution to future bandwidth requirements in the Tb/s range. Recently, a number of free-space optical interconnects (FSOI) has been demonstrated based on wafer-level flip-chip bonded or reflecting prism devices [2][3][4][5][6]. In order to sustain low channel crosstalk and high emitter-to-detector coupling efficiency, tight tolerances on optical alignment of FSOI parts lead to time consuming and expensive fabrication techniques [7][8].…”