THE Optical Interconnects - IEEE Xplore

IEEE JOURNAL OF SELECTED TOPICS IN QUANTUM ELECTRONICS, VOL. 9, NO. 2, MARCH/APRIL 2003

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Introduction to the Issue on Optical Interconnects

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HE Optical Interconnects field has experienced a continuous push into applications with ever-shorter transport path lengths. This drive started only a brief time after the widespread deployment of long-haul optical fiber began about 25 years ago, and has been accelerating ever since. Significant optical interconnect research and development activities now span a length-scale of about seven orders of magnitude, ranging from dense wavelength division multiplexing-based long-haul transport, routing, and switching—for signal transport in the hundreds of kilometers range, to dense device integration for chip-scale interconnects—where path lengths are on the order of centimeters. The motivation for this trend stems from the widening mismatch in performance scaling between silicon-based electronic switching speeds and densities, and the metal-based interconnection fabrics needed to keep pace with them. The hope is that the steady advances being made in integrated optical electronics (OE) array technology can be exploited to overcome the interconnect bottlenecks of metal-based technology and sustain the exponential silicon-chip-based performance growth in computing and communications systems. The limitations of metal interconnects at the board, backplane, and box-to-box levels are already affecting the overall system performance scalability for many applications. This has resulted in significant inroads for optical interconnect technology in the box-to-box and backplane domains. These achievements are based on advancements in the packaging of parallel optical transceivers with guided wave optical channels that enable higher bandwidth densities and efficiencies as compared to their metal-based competitors. As silicon IC technology continues its march toward deep-submicron feature sizes, it is widely recognized that the interconnect fabric will be the critical source of performance bottlenecks at the intrachip level. A key question is, therefore, whether and how the optical interconnect trend will continue at the board-, interposer-, and chip-level interconnect domains. A consequence of the wide transport-length range in optical interconnect applications now under consideration is a commensurately wide diversity in research and development. Efforts now underway range from basic material and device research, to integration and packaging research and development, to system- and architecture-level design efforts and studies to determine efficient ways to exploit optical interconnect technology at each level. Perhaps the only common theme in optical

Digital Object Identifier 10.1109/JSTQE.2003.814943

interconnect research and development is a focus on efficient packaging—which seems to play a critical roll in the cost and performance of optical interconnect approaches at all levels. This special issue was developed to highlight the latest research and development progress across the entire range of existing and projected optical interconnect applications. The eight invited and 24 contributed papers truly exemplify the current diversity of work in optical interconnects. We have divided the papers into five general areas to delineate key thrust areas, recognizing that there is significant overlap in some papers. The first section, Device Integration and Packaging, contains papers that focus on issues associated with integrating active and passive OE devices for effective implementation of interconnection fabrics. The papers cover topics that range from large, high-density arrays of OE transceivers that are integrated with silicon very large scale integration for free-space optical interconnect concepts to moderate density integrated devices for parallel fiber interconnects or free-space applications, to novel techniques for clock and signal distribution and heterogeneous integration at the chip-scale. The second and largest section of this special issue is entitled Chip-scale Optical Interconnects. The wide-ranging papers in this section cover issues associated with inter- and intrachip interconnects. Important topics covered in this section include performance analysis and modeling for on-chip and interchip interconnects, implementation of multichip module/interposer packages to enable optical interconnects and the use of mode-locked sources in optical interconnects. The papers of the third section of this issue are focused on Free-space Optical Interconnects. Included are papers covering issues associated with the effective implementation of dense arrays of OE input/output (I/O) in optically interconnected free-space fabrics for parallel chip-to-chip interconnection and arrays of chips for global interconnection fabrics. Also included are papers describing novel applications of free-space optical interconnects for router scheduling and biosequence analysis. The fourth section of this issue is dedicated to MEMS-Mirror Cross-connects. The papers range from a description of near-term design and performance characteristics for a large switch, to newer designs based on white cells and double-sided mirrors. The last section of this special issue is dedicated to papers concerned with Optical Interconnect System and Architecture issues. The wide-ranging papers include a general discussion of the prospects for optical interconnects “in the box,” specific interface card and forward error correction design and implementation issues for optical links, and new architectural notions for parallel computer interconnects.

1077-260X/03$17.00 © 2003 IEEE

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MICHAEL W. HANEY, Guest Editor University of Delaware, Department of Electrical and Computer Engineering, Newark, DE 19716 USA HUGO THIENPONT, Guest Editor Vrije Universiteit Brussels Applied Physics & Photonics, TW-TONA, Pleinlaan 2, Brussels B-1050, Belgium

ACKNOWLEDGMENT The editors are very grateful to the authors for their diligence in putting their manuscripts together in a timely manner, and to the many reviewers who provided thoughtful guidance that amplified the quality of the papers in this issue. They are especially thankful to Janet Reed and Linda Matarazzo for their dedication, good humor, and professionalism in overcoming the unexpected challenges that arose in putting this special issue together.

TETSUZO YOSHIMURA, Guest Editor Department of Electronics and Bioelectronics Tokyo University of Technology Hachioji, Tokyo 192-0982, Japan

Michael W. Haney (M’80) received the B.S. degree in physics from the University of Massachusetts, Amherst, in 1976, the M.S. degree in electrical engineering from the University of Illinois, Urbana–Champaign, in 1978, and the Ph.D. degree in electrical engineering from the California Institute of Technology, Pasadena, in 1986. From 1978 to 1986, he was with General Dynamics, where his work ranged from the development of electro-optic sensors to research in photonic signal processing. In 1986, he joined BDM International, Inc., where he became a Senior Principal Staff Member and the Director of Photonics Programs. In 1994, he joined George Mason University as an Associate Professor of electrical and computer engineering. In 2001, he moved to the University of Delaware, Newark, as a Professor of electrical and computer engineering. His research activities are focused on the application of photonics to new computing, switching, and signal processing architectures. Prof. Haney has chaired and co-chaired several technical conferences and is a previous Chairman of the IEEE Communications Society’s Technical Committee on Interconnections Within High-Speed Digital Systems. Dr. Haney is a Fellow of the Optical Society of America and a member of the IEEE Communications and Lasers & Electro-Optics Societies.

Hugo Thienpont (M’97–A’97) was born in Belgium, in 1961. He graduated from the Vrije Universiteit Brussels, Brussels, Belgium, in 1984 as an electrical engineer with majors in applied physics and applied optics. In 1994, he became Professor in the Faculty of Applied Sciences, Vrije Universiteit Brussels, Brussels, Belgium, with teaching responsibilities in six compulsory photonics courses. Today, he is Director of Research of the Laboratory for Photonics and is Promoter of different photonics related research and industrial projects. His research activities comprise materials, modeling, components and devices, packaging, and demonstrators for photonic interconnects in computing. Prof. Thienpont serves on technical program committees of several EOS, IEEE, OSA, and SPIE topical and annual meetings and was Technical Program Chair of the ICO/EOS topical meeting Optics in Computing’98. He is an Associate Editor of Optical Engineering, and was Guest Editor of the special issues on Optics in Computing for the Journal of the EOS in 1998, the OSA journal Applied Optics, in 2000, and for the International Journal of Optoelectronics on Tutorials on Optics in Computing. He received the ICO International Prize for his contributions in the field of optical and photonic information processing in 1999.


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Tetsuzo Yoshimura (M’00) was born in Tokyo, Japan, on October 28, 1951. He received the B.Sc. degree in physics from Tohoku University, Sendai, Japan, in 1974 and the M.Sc. and Ph.D. degrees in physics from Kyoto University, Kyoto, Japan, in 1976 and 1985, respectively. In 1976, he joined Fujitsu Laboratories Ltd., Kawasaki, and was engaged in optoelectronic device research including nonlinear optical circuits and mono-molecule-controlled organic film growth methods such as molecular layer deposition. From 1997 to 2000, he was with Fujitsu Computer Packaging Technologies, Inc., San Jose, CA, in charge of researches on board-level optical interconnects, followed by an activity in Electronic SI Technology Research Department of ASET. He is currently a Professor in the Department of Electronics and Bioelectronics, Tokyo University of Technology, Tokyo, Japan, and is engaged in researches on self-organized microoptoelectronic systems, resource-saving microsystem integration processes, and molecular nanotechnologies. Prof. Yoshimura is a Member of the IEEE Lasers & Electro-Optics Society and the Japan Society of Applied Physics.