Thomas J. Cloonan

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>>

Photonic switching applications of 2-D and 3-D crossover networks based on 2-input, 2-output switching nodes

Optical implementations of both 2-D and 3-D crossover networks are described, and we show that these networks can be used for connecting multiple stages of 2-input, 2-output switching elements. We also show that simple conversion steps can be used to convert 2-D crossover networks into 3-D crossover networks. Both network types can be implemented with low loss optical imaging systems, and we show that the same optics can be used to implement the intranode connections and the internode for various types of 2-input, 2-output switching elements. In addition, we discuss the difficulties that arise when the same optical hardware is applied to switching elements of larger dimensionality.

Optical design of a digital switch.

An optical design of a time multiplexed nonblocking space switch is described for optically nonlinear arrays of logic devices interconnected in free space. Regular interconnects in the form of crossovers are used for interconnecting optical logic devices, and some efficiency is lost due to the strict use of regular interconnects. It is shown that for this application, the higher component count is comparable with the component count for the electronic implementation of the switch. We maintain that for a high bandwidth application such as packet switching, simple bulk optics provides a suitable medium for interconnecting optical logic devices even at high speeds, and that a more elaborate approach is not warranted.

Optical Implementation And Performance Of One-Dimensional And Two-Dimensional Trimmed Inverse Augmented Data Manipulator Networks For Multiprocessor Computer Systems

Two classes of 0(N log(N)) network architectures known as one-dimensional trimmed inverse augmented data manipulator networks and two-dimensional trimmed inverse augmented data manipulator networks are described. These network architectures, which are derived from augmented data manipulator networks, may find potential applications as optical interconnection networks for multiprocessor computer systems. Comparisons between the network types are made based on hardware complexity and blocking probability. It is shown that pairs of extra stages (added to the input end and the output end of the networks) and the extra connectivity provided by two-dimensional optical interconnections can improve blocking probability if an increase in hardware cost is permissible. A potential optical implementation of the network, which uses computer-generated binary phase gratings, is described.

4/spl times/4 arrays of FET-SEED embedded control 2/spl times/1 optoelectronic switching nodes with electrical fan-out

We describe a 4 by 4 array of embedded control two input, one output optoelectronic switching nodes based on the field effect transistor self electro-optic effect device (FET-SEED) technology. The arrays have electrical fan-out to remove the loss associated with optical fan-out in the system application. Extensive testing was done on several arrays at 156 Mb/s per channel with optical switching energies below 100 fJ, with the output driver limiting the maximum data rate to 400 Mb/s. Power dissipation, noise margin, crosstalk, sensitivity to stray light, and uniformity of both threshold and output waveforms are also discussed.<<ETX>>

Comparative study of optical and electronic interconnection technologies for large asynchronous transfer mode packet switching applications

The hardware and power requirements for a large asynchronous transfer mode packet switch that is implemented using several different mixes of optical and electronic (metallic) interconnections are studied. The optical interconnections are based on free-space digital optics, and the metallic interconnections are based on state-of-the-art electronic packaging technologies. The advantages and disadvantages of each of the different interconnection technologies are explored. These results should help researchers identify the areas that require improvement within each of the technologies. They should also be useful to designers of future systems who must select an appropriate interconnection and packaging technology.

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.

Topological equivalence of optical crossover networks and modified data manipulator networks

The crossover network is a multistage interconnection network that shows potential for use in optical computing and photonic switching applications. In this paper, a proof of topological equivalence between the crossover network and the modified data manipulator network is presented. It is shown that the Gray Code can be used as the mapping function between the crossover network and a network which is equivalent to the modified data manipulator network. Given the results of this proof, the optical crossover network can then be proposed as the optical interconnection fabric for many switching and computing applications.

Shuffle-equivalent interconnection topologies based on computer-generated binary-phase gratings

Several different shuffle-equivalent interconnection topologies that can be used within the optical link stages of photonic-switching networks are studied. These schemes include the two shuffle, the two banyan, and the segmented two shuffle, which can be used to interconnect two-input, two-output switching nodes. The schemes also include the four shuffle and the four banyan, which can be used to interconnect four-input, four-output switching nodes. (Note: The segmented two shuffle and the four banyan are novel interconnection topologies that were developed to satisfy some of the constraints of free-space digital optics). It is shown that each of these interconnection topologies can be implemented by the use of relatively simple imaging optics that contain space-invariant computer-generated binaryphase gratings. The effects of node type and interconnection topology on the laser power requirements and the optical component complexity within the resulting systems are also studied. The general class of networks nown as extended generalized shuffle networks is used as a baseline for the analysis. It is shown that (2, 1, 1) nodes and (2, 2, 2) nodes connected by two-banyan interconnections can produce power-efficient and cost-effective systems. The results should help identify the architectural trade-offs that exist when a node type and an interconnection topology are selected for implementation within a switching system based on free-space digital optics.

An all-optical realization of a 2*1 free-space switching node

An experimental all-optical 2*1 free-space switching node that was implemented with semiconductor laser diodes, beam splitters, retardation plates, lenses, mirrors, dichroic filters and binary phase gratings is demonstrated. Two symmetric self-electrooptic effect device arrays used as optical logic elements were cascaded. Two electronically controlled optical signals were used to determine the switch routing. The 2*1 node transmitted at a data rate of 5 kb/s.<<ETX>>