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.>

Photonic technologies are reviewed that could become important components of future telecommunication systems. Photonic devices and systems are divided into two classes according to the function they perform. The first class, relational, refers to devices, that map the input channels to the output channels under external control. The second class, logic, perform some type or combination of Boolean logic functions. Some of the strengths and weaknesses of operating in the photonic domain are presented. Relational devices and their applications are discussed. Optical logic devices and their potential applications are reviewed.>

A speaker independent isolated word speech recognition system is developed based on computer generated phonemes (CGP). A CGP is a vector of features that has been generated to represent a region of speech. The CGP creation algorithm looks for stable sounds in the incoming word through the use of a similarity measure. When a stable sound is detected a CGP is created to represent it. In addition to the creation of CGPs for stable vocal tract sounds, when unvoiced fricatives occur at either the beginning or end of a word a representative CGP is created. Using a heavily constrained dynamic time warping algorithm, the CGPs of the incoming word are then compared against reference templates, which consist of previously created strings of CGPs. The identity of the reference template which is closest in distance to the incoming test word is chosen as the estimate of the test word.