We describe a technique for assembling fiber bundle arrays as needed in optical computing and photonic switching systems. Two 4x4 arrays with single-mode and multimode optical fibers were manufactured. Fiber ends were located to within 3 mu m of their ideal position and to a pointing precision of 30 arcmin. A third 4x8 array was manufactured with single-mode fibers, and fiber ends were located to within 1.5 mu m of their ideal position.

The design, construction, and operational testing of a five-stage, fully interconnected 32 × 16 switching fabric by the use of smart-pixel (2, 1, 1) switching nodes are described. The arrays of switching nodes use monolithically integrated GaAs field-effect transistors, multiple-quantum-well p-i-n detectors, and self-electro-optic-device modulators. Each switching node incorporates 25 field-effect transistors and 17 p-i-n diodes to realize two differential optical receivers, the 2 × 1 node switching logic, a single-bit node control memory, and one differential optical transmitter. The five stages of node arrays are interconnected to form a two-dimensional banyan network by the use of Fourier-plane computer-generated holograms. System input and output are made by two-dimensional fiber-bundle matrices, and the system optical hardware design incorporates frequency-stabilized lasers, pupil-division beam combination, and a hybrid micro-macro lens for fiber-bundle imaging. Optomechanical packaging of the system ut lizes modular kinematic component positioning and active thermal control to enable simple rapid assembly. Two preliminary operational experiments are completed. In the first experiment, five stages are operated at 50 Mbits/s with 15 active inputs and outputs. The second experiment attempts to operate two stages of second-generation node arrays at 155 Mbits/s, with eight of the 15 active nodes functioning correctly along the straight switch-routing paths.

A 5 stage, fully interconnected 32/spl times/16 switching network using smart pixel 2/spl times/1 switching nodes is demonstrated. The system was designed to operate with 150 Mbps data rates.< >

We describe the design and demonstration of an extended generalized shuffle interconnection network, centrally controlled by a personal computer. A banyan interconnection pattern is implemented by use of computer-generated Fourier holograms and custom metallization at each 32 × 32 switching node array. Each array of electrically controlled tristate symmetric self-electro-optic-effect devices has 10,240 optical pinouts and 32 electrical pinouts, and the six-stage system occupies a 9 in. × 12.5 in. (22.9 cm × 31.7 cm) area. Details of the architecture, optical and mechanical design, and system alignment and tolerancing are presented.

We demonstrate a 5 stage, fully interconnected 32×16 switching network using smart pixel 2×1 switching nodes. A 15input, 16 output system configuration was operated at 50 Mb/s per channel.

A series of experiments has been performed to determine the critical practical issues in high-density free-space optically interconnected systems. Some ofthese experiments have implemented switching fabrics by optically interconnecting 2-D arrays of symmetric seif-electro-optic effect devices (S-SEEDs). In the first, three 16 x 8 arrays of S-SEEDs, all operating as logic gates, were optically interconnected, and in the last experiment, afully interconnected switching fabric using six 32 x 32 S-SEED arrays was demonstrated. The practical realization of this technology represents a challenge to modern optomechanics because ofthe required optical resolution, mechanical precision, stability, and number of components involved. A comparison of these experimental systems shows that significant optical power loss may be incurred when theoretically "lossless" techniques are actually implemented, mainly because of the system complexity. The use of much simpler techniques is shown to dramatically decrease system assembly and alignment times and increase system stability, with similar overall loss. The tolerancing analysis used in these systems shows thatthe worst-case optical constraints result in mechanical tolerances in the micrometer to submicrometer range. The successful operation of these systems demonstrates the ability of relatively simple optical and mechanical techniques and materials to meet these tolerances.

Free-space optical interconnections offer a means to alleviate many high speed, high density communications problems in digital systems. The realization of this new technology involves the application of many classical optical testing techniques, as well as the development of several novel tools and techniques. We describe the design and implementation of a free-space optically interconnected switching fabric, and the fabrication and testing techniques involved. The lenses, polarizing beam-splitters, lasers, and diffractive optics used in the experiment were tested for optical transmission efficiency and uniformity, and wavefront quality.

The high throughput of optical interconnections was first utilized in the long distance telecommunication network. With advances in technology, optical communication continues to penetrate to ever shorter interconnection distances. Free-space optical interconnections at the chip and gate level can enhance the performance of electrical connections since light can exploit the dimension perpendicular to the planar electronic surface and can overcome the impedance losses typically experienced by high speed electronic signals.

A prototype digital free-space photonic switching fabric is demonstrated. It consists of three cascaded 16 x 8 arrays of symmetric self-electro-optic-effect devices that are used as logic gates that implement part of a multistage interconnection network. We discuss architecture, device tolerancing, optical system design, and optomechanical design. This optical circuit is successfully configured as a fully operational array of 32 independent 2 x 2 nodes and operates at 100 kHz.

Designers of future switching networks (both packet and circuit switches) will encounter many packaging and interconnection problems as data rates and network sizes continue to increase. Free-space digital optics is a new interconnection technology that may circumvent many of these predicted problems by using beams of light to transmit information between integrated circuits. The technology is described, and its advantages are outlined. New network architectures, such as the extended generalized shuffle (EGS) networks, that capitalize on the features of optics are described. A description of the current generation of prototype systems is given to illustrate the current state of the art

Two-dimensional arrays of logic self-electrooptic effect devices (L-SEEDs), consisting of electrically connected quantum-well p-i-n diode detectors and modulators are demonstrated. The topology of the electrical connections between the detectors is equivalent to the connections between transistors in CMOS circuits. Three different L-SEED arrays were built and tested. Each element in one array can implement any of the four basic Boolean logic functions (i.e., NOR, NAND, AND, OR). Each element in the second L-SEED array can implement the function E=AB+CD. The third L-SEED array consists of 32*16 arrays of symmetric SEEDs (S-SEEDs) connected with optoelectronic transmission gates. Photonic switching nodes, multiplexers, demultiplexers, and shift registers have been demonstrated using this array. >

Parts of a multistage switching network were implemented by optically interconnecting arrays of symmetric self electro-optic effect devices. In an experiment completed last Spring, three 16 X 8 arrays of S-SEEDs, all operating as logic gates, were optically connected. A fully-interconnected switching fabric using six 32 X 32 S-SEED arrays is currently being tested. These are the latest in a series of experiments to investigate and develop this technology, and they substantially involve optomechanics. The practical realization of this technology represents a challenge to modern optomechanics due to the required precision, stability, and number of components involved. An overview of free-space photonic switching and the required experimental hardware subsystems is presented, followed by details of the optical systems to interconnect the switching device arrays and the mechanical systems which locate and position the optics and devices. The tolerancing analysis used in these systems is reviewed and comparisons between the two systems are made.

Practical free-space photonic switches and optical processors require the development of high performance optical and optomechanical systems.1 Desirable attributes include low costs, compact size, ease of alignment, high mechanical and thermal stability, low component count, low wavefront aberration, high optical throughput, modularity for maintenance and repair, and low signal nonuniformity.2 We present an optical and optomechanical system design that addresses these goals. We have demonstrated the cascaded operation of two 64 × 32 arrays of S-SEEDs, providing 4096 optical interconnections between the two arrays. This compact (9 × 13 in.) and stable system is used in implementing of a fully interconnected six-stage banyan network.

We implemented part of a multistage switching networkby optically interconnecting three 16 × 8 symmetric-self-electro-opticeffect-device (S-SEED) arrays. The inputs consisted of 64 data and 64 control signals, which were first converted to differential format, fanned out by 2, and then switched through an array of 64, 2×1 switching nodes. The data inputs were generated by a matrix of 64 fibers and identical control signals were sent to all 64 switch nodes by a control laser and an 8 × 8 binary-phase grating. The S-SEEDs have 5×10µm windows on a 20µm pitch, and they were operated as arrays of NAND and NOR gates. Crossover interconnections were used both between and within switch node stages. Logic-level nonuniformity and noise-margin difficulties that were present in an earlier experiment1 have been reduced, and fully functional, relatively stable operation has been achieved. Details of the architecture, optical hardware, and system performance will be presented.

The authors have detailed some of the ways in which the specification of each component of a digital free-space photonic switch are coupled. Such systems may ultimately be capable of providing massive connectivity of high speed signals. The production of large 2-dimensional arrays of optical devices which are cascadable has enabled a new technology. This is a recent development. Consequently, only a few free-space digital optical circuits have been constructed. The systems operate with a performance well below that achievable with conventional electronics. However, their construction validates the confident prediction of the feasibility of more viable full scale systems. It also enables the assessment of both components and architectures in a test-bed system, providing feedback to improve individual aspects of the overall system

The demonstration of a digital, free-space switching fabric will be described[l,2]. It consists of three cascaded 16x8 arrays of Symmetric Self Electro-Optic Effect devices (S-SEEDs)[3]. The first array of bistable devices implement the input interface. The other two arrays operate as two-input logic gates with a fan-out of two. Crossover interconnects are implemented between the arrays[4]. The correct operation of the circuit results in the implementation of an array of 32 independent 2x2 nodes.

We demonstrate a prototype digital free-space photonic switching fabric consisling of three cascaded 16x8 arrays of Symmetric Self Electro-optic Effect Devices used as logic gates. 1.© (1991) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.