Frank A. P. Tooley

Optical Interconnections Using Microlens Arrays

Free-space interconnection of widely spaced pixels may be implemented using microlenses, rather than conventional imaging. Advantages, problems, and studies of system capacity are discussed.

Free-space digital optical systems

Within the past 15 years there has been significant progress in the development of two-dimensional arrays of optical and optoelectronic devices. This progress has, in turn, led to the construction of several free-space digital optical system demonstrators. The first was an optical master-slave flip-flop using Hughes liquid-crystal light valves as optical logic gates and computer-generated holograms as the gate-to-gate interconnects. This was demonstrated at USC in 1984. Since then there have been numerous demonstrations of free-space digital optical systems including a simple optical computing system (1990) and five switching fabrics designated System/sub 1/ (1988), System/sub 2/ (1989), System/sub 3/ (1990), System/sub 4/ (1991) and System/sub 5/ (1993). The main focus of this paper will be to describe the five switching fabric demonstrators constructed by AT&T in Naperville, IL. The paper will begin with an overview of the SEED technology which was the device platform used by the demonstrators. This will be followed by a discussion of the architecture, optics, and optomechanics developed for each of the five demonstrators. >

Six-stage digital free-space optical switching network using symmetric self-electro-optic-effect devices

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.

Experimental investigation of a free-space optical switching network by using symmetric self-electro-optic-effect devices.

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.

An all-optical implementation of a 3-D crossover switching network

One of the more promising interconnection schemes proposed for use in photonic switching networks is the crossover interconnection network; however, reported implementations of the crossover have been limited in size and complexity. A large-scale cascadable implementation of the optical crossover network that capitalizes on planar symmetric self electrooptic effect device (S-SEED) arrays is discussed. A fully functional experimental prototype with 32 inputs and 32 outputs that was operated at a maximum rate of 55.7 kb/s is also discussed. It is also shown that S-SEED arrays can be operated as simple two-input two-output nodes (called 2-modules) within a controllable network.<<ETX>>

Optomechanics of a free-space photonic switching fabric: the system

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.

Optomechanics of a free-space photonic switch: the components

We will discuss the optomechanical design of components used for free space optical switch prototypes built to develop potential solutions for the high-speed digital switching problems of bandwidth, interconnection, and density. In our free space optical switching fabrics, arrays of light beams propagate between array of optical transceiver devices called Symmetric Self Electro-Optic Effect Device (S-SEED). These arrays have been operated with more than a thousand beams incident on device windows typically 5 microns in diameter. To image the arrays required high resolution optics, tight component tolerances, and stable mounting techniques. This paper explains the optomechanical design and construction of the components of the free space optical switching fabric, designed under requirements of small size, high resolution of movement, mechanical stability, and minimal cost. Comparisons are made between two versions of experimental components, including S-SEED mounts and mounting plates.

A 3D Crossover Switching Network Based on S-SEED Arrays

This paper describes a fully-operational prototype of an optical crossover network that was based on S-SEED arrays. The network provided for 32 input ports and 32 output ports, and it was operated at a maximum channel rate of 55.7 kbps. New node-types (2-modules) and 2D to 3D transformations of crossover networks are also discussed.

Construction and tolerancing of an optical-CLIP

An all-optical processing loop circuit, pumped entirely by semiconductor diode lasers, has been constructed and operated. Functional features include optically programmable logic, thresholding, and synchronization; these are achieved using three bistable interference filter devices. The circuit is presently single-channel, however 15 x 15 capability of the devices has been demonstrated using Dammann holograms and array-to-array coupling of a pair of bistable plates; potential parallelism is in excess of lO. Circuit simulations and tolerancing are also described.

Optical polymer for photonic integration

Development of a novel multifunctional acrylate based photo- polymer for photonic integration is presented. A 325 nm He:Cd laser has been used for direct writing of 50 micrometers square core multi-mode waveguides, compliant bumps for flip- chip bonding and 45 degrees total internal reflection mirrors for out of plane coupling. The transmission losses are measured to be 0.17 dB/cm at 850 nm and 0.5 dB/cm at 1300 nm by cutback method. Partially halogenated versions show losses around 1dB/cm at 1550 nm. DTA-TG analysis shows that this multifunctional acrylate co-polymer is thermally stable up to a temperature of 270 degrees C.