An adaptive alignment scheme for packaging two-dimensional (2D) arrays of optoelectronic systems interconnected by free-space optics is presented. A method of using three quadrant detectors to detect alignment errors in six degrees of freedom is described. However, the complexity of this system increases due to the interactions among the detected error signals. A novel control algorithm is presented to eliminate the interaction and simplify the design of the closed-loop feedback control. A computer simulation compares different algorithms and shows the effectiveness of the proposed algorithm. An experimental closed-loop feedback system demonstrated the principle of the error detection and correction of the proposed system with initial errors in multiple degrees of freedom

The concept of adaptive optics for improving the cost-performance of free-space optoelectronic interconnects is discussed. Adaptive optics as a design option for optical interconnect systems is presented and discussed. A practical demonstrator that performs low-order correction was built and tested. Slowly varying misalignments, including thermal effects, were compensated for in a 622-Mbit/s free-space optical data link.

Providing free-space optical interconnects and the integration of a 2-D optoelectronic interfaces with silicon chips (smart-pixels) can allow many advantages over convention interconnects. However, the introduction of free-space optics brings new technological difficulties for the system designer, mainly concerned with the system packaging. Active alignment is an important design option to achieve realistic low-cost free-space optical interconnects [1].

The integration of 2-D optoelectronic interfaces with silicon chips, employing what is known as smart-pixel technology, can overcome many of the foreseen limitations of conventional interconnects [1]. The solution is to provide free-space optical interconnects operating at the silicon on-chip clock-rate and with the numbers required to yield the necessary aggregate bandwidth. To investigate the application of this approach to parallel information processing we have been building an optoelectronic data sorting machine as a system demonstrator. The architecture of the optoelectronic sorter and the design of the components was described previously [2].

Low-order adaptive optics is a design option to achieve realistic low-cost free-space optical interconnects. We are investigating the issues using a system demonstrator.

Free-space optical interconnects have been identified as a potentially important technology for future massively parallel-computing systems. The development of optoelectronic smart pixels based on InGaAs/AlGaAs multiple-quantum-well modulators and detectors flip-chip solder-bump bonded onto complementary-metal-oxide-semiconductor (CMOS) circuits and the design and construction of an experimental processor in which the devices are linked by free-space optical interconnects are described. For demonstrating the capabilities of the technology, a parallel data-sorting system has been identified as an effective demonstrator. By use of Batcher's bitonic sorting algorithm and exploitation of a perfect-shuffle optical interconnection, the system has the potential to perform a full sort on 1024, 16-bit words in less than 16 mus. We describe the design, testing, and characterization of the smart-pixel devices and free-space optical components. InGaAs-CMOS smart-pixel, chip-to-chip communication has been demonstrated at 50 Mbits/s. It is shown that the initial system specifications can be met by the component technologies.

To someone with an electronics or computer science background, many of optical computing's concepts may seem outlandish. Optics grew out of applied physics and still retains many aspects of that heritage. This is in contrast to digital computing's roots in electronics. Recent efforts have been made to bring optical computing more in line with microelectronic engineering. Perhaps that will speed the acceptance of opto-electronic technology. The authors describe their research into optical devices for data communication. They are investigating free-space optics, the propagation of optical signals through the air using lenses and mirrors to focus and redirect the beams. The advantages of free-space optics, derive from their large spatial bandwidth and physical channel density. Like the human eye, which takes in an enormous amount of information in parallel, a low-cost lens can provide more than a million independent connections. The authors aim to exploit optoelectronic computing's capability for such massively parallel data transfers.