Scott A. Hamilton was born in Ridgecrest, CA on March 10, 1970. He studied electrical engineering and received the B.S. degree with high honors from the University of California, Davis in 1993. He continued on as a graduate student at UC Davis and earned the M.S. and Ph.D. degrees in electrical engineering in 1996 and 1999. As a graduate student, Dr. Hamilton worked with Professors André Knoesen and Diego Yankelevich to develop wideband high-linearity polymer modulators for RF-photonic links. From 1989 to 1998, he worked for the Aircraft Systems Engineering Branch at the Naval Air Warfare Center in China Lake, CA. In 2000, Dr. Hamilton joined the Optical Communications Technology Group at MIT Lincoln Laboratory where he is conducting research on ultrafast all-optical packet routing and free-space laser communication. His research interests include high-sensitivity lasercom, high-speed short-pulse communication systems, ultrafast optical signal processing, nonlinear optics, and integrated microphotonics. Dr. Hamilton is an associate editor for the IEEE Journal of Quantum Electronics. He is also a member of the IEEE Lasers and Electro-Optics Society (LEOS) Optical Communications and the Optical Communication Conference (OFC) Fibers and Optical Propagation Effects program subcommittees, the IEEE Electron Devices Society (EDS) committee on Optoelectronic Devices, the Optical Society of America, and the IEEE.

Free-Space Communication Techniques for Optical Networks
Free-Space Communication Techniques for Optical Networks was one of the featured topics at this year’s IEEE LEOS Summer Topical Meeting. It is a dynamic field and today, free-space laser systems are considered viable solutions for high-capacity network applications ranging from last-mile connectivity and mobile infrared networking in the local area, to cost-effective inter-office-building metropolitan connections, to reconfigurable inter-satellite wide-area networking for commercial and military applications. Due to the short wavelength used in free-space laser communications systems, many advantages are realized in transmission power, beam directivity, and antenna (telescope) size, as compared to RF solutions. System demonstrations and critical technology for ultra long-haul free-space laser communication applications are being developed on a global scale. In the United States, the Department of Defense is developing a wide-area satellite network interconnected by optical links and the National Aeronautics and Space Administration (NASA) is working to extend lasercom technology to enable high data rate communications throughout the solar system. In addition, the European Space Agency has demonstrated a functional optical inter-satellite link and, through a collaboration with the Japan Aerospace Exploration Agency, achieved an optical link between a ground-based transceiver and a geostationary satellite.
Located on the beautiful Shelter Point marina in San Diego, the conference provided a venue for attendees to meet and discuss the status of research and development in high-capacity free-space laser communications. The conference began with a plenary talk given by Professor Larry Andrews from the University of Central Florida on the theory of free-space laser propagation and atmospheric effects. During his talk, Professor Andrews gave an insightful overview of his work to develop theoretical models for optical scintillation and beam wander effects which can result in severe communication penalties for free-space optical terrestrial links and ground-to-satellite links.
Many of the invited papers discussed system aspects of free-space optical communication links. The system application that received the most attention at the conference was the Mars Laser Communication Demonstration (MLCD) sponsored by NASA. Among the invited speakers, Dr. Don Boroson, Joe Scozzafava, Dr. Chien-Chung Chen, and Lawrence Candell provided exciting overviews of the system engineering challenges, end-to-end link design, and transmitter/receiver hardware that will be utilized to demonstrate optical communication between Mars and Earth. Dr. Bryan Robinson presented an experimental demonstration of a photon-counting link with world record multiple-bit-per-photon sensitivity for extreme power-limited optical communication applications. Professor Alan Willner described the challenges faced by inter-satellite networking and the potential for wavelength-division multiplexing (WDM) techniques to realize reconfigurable high-capacity packet routing. For applications a little closer to home, Professor Tony Acampora discussed the capacity and mobility management issues associated with last-mile business and residential ultra-broadband free-space terrestrial mesh networks. Finally, Dr. Gary Shaw described distributed terrestrial sensor networks that utilize the atmospheric scattering associated with ultraviolet wavelengths to achieve communication between sensors with non-line-of-sight transmit-receive geometries.
Components and subsystems were the focal point of the remaining invited speakers. Dr. Simon Verghese discussed InGaAsP Geiger-mode avalanche-photodiodes that can be integrated in a compact receiver configuration and are capable of digital output levels after detecting individual photons. William Farr presented a broad view of many different photon-counting detectors and compared their performance in terms of sensitivity, noise contribution, and practicality for photon-counting communication applications. Dr. Keith Wilson described the impressive performance gain offered by using adaptive optics to compensate for atmospheric effects on a lasercom downlink in order to enable telescope-pointing angles within 3 degrees of the sun. Dr. Hamid Hemmati described the difficult challenges associated with pointing a narrow laser beam over interplanetary distances and how accurate deep-space transmitter pointing can be achieved by Earth-image tracking using near-infrared radiation. Yoshinori Arimoto discussed a lightweight compact lasercom transceiver that successfully demonstrated pointing and tracking between a mobile high-altitude air-ship and a ground terminal. Dr. Neal Spellmeyer described the challenges and technical design used to successfully demonstrate a low-duty-cycle high-power variable-rate pulse-position modulation transmitter for deployment in deep-space lasercom applications. Finally, Berry Smutny discussed the daunting challenges faced in deploying lasercom inter-satellite network terminals and presented a technical overview of beaconless coherent terminals that will be deployed in 2006.
This LEOS Newsletter features both extended-versions and re-prints of the invited conference papers. As you will see, free-space optical communication technology has come a long way. The applications that are under development today range in scale from tiny low-power on-chip interconnects to interplanetary networks interconnected with high-rate lasercom links. It remains, however, a field where much exciting research is left to be done. I believe that we will continue to see more ground-breaking demonstrations of free-space device technology and future optical system demonstrations.
As a final note, I would like to thank the invited and contributed speakers for giving excellent presentations on exciting work, the conference attendees for their interest and participation, the technical program committee members for their help in getting good invited speakers to attend the conference, and Mary Hendricx at LEOS for her hard work and organizational skills that led to a wonderful event in which a good time was had by all.