Making A Many-Colored Processing Engine:
Signal Processing with Optical Filters

Seminar by
Dr. Christi Madsen,
Texas A & M Univ.

Abstract: The ultimate information capacity of optical fibers is far beyond currently deployed systems even with the exponential growth in system capacity over the past 20 years. Even now, the performance of high-capacity, long-distance wavelength-division-multiplexed (WDM) networks depends significantly on reconfigurable optical filters for bandwidth management and adaptive filters for compensating analog impairments. Optical filters are also key elements in optical code generation and detection with applications in optical packet header processing. Whether the end goal is for communications or high-speed signal processing, optical filters that can operate on amplitude, phase and polarization are critical to unleashing the full potential of optical systems. To be practical, a cost-effective implementation that can scale in optical circuit integration density and functionality is required. This talk addresses optical filters in the context of their analog and digital relatives. I will show how well-known filter types are related to the underlying interference mechanisms and how digital filter theory concepts are beneficially translated to the optical domain. Then, the present capabilities of integrated optics for implementing adaptive optical filters and an overview of some challenges ahead will be discussed. Adaptive filters implemented using high index-contrast silica-on-silicon planar waveguides with applications to tunable chromatic dispersion compensation and polarization monitoring, control and polarization mode dispersion compensation will be used as examples. With state-of-the-art integrated optical filters, we have the ability to realize a many-colored, high-speed and cost-effective processing engine that truly harnesses the power of photonics.

Bio: Christi Madsen received the Bachelor’s degree from The University of Texas at Austin in 1986, the Master’s degree from Stanford University, Stanford, CA, in 1987, and the Ph.D. degree from Rutgers University, Piscataway, NJ, in 1996, all in electrical engineering. She joined AT&T Bell Laboratories in 1987 and worked for the submarine systems business unit. After completing her Ph.D., she transferred to the integrated photonics research department at Bell Laboratories. Since then, her research has focused on the application of digital filter and signal processing techniques to optical filters for high-speed, high-capacity optical communication systems. In 1998, Madsen invented a class of tunable, multi-stage optical allpass filters that allow any phase response to be approximated and have application in chromatic dispersion compensation and polarization mode dispersion compensation. She has given a short course on “Optical Filters for WDM Systems: Theory, Technologies, and Applications” at OFC and was the 2004 General Chair for the Integrated Photonics Research (IPR) Conference. She was promoted to Distinguished Member of the Technical Staff at Bell Laboratories in 2002 and achieved Fellow ranking in the Optical Society of America in 2003. She holds 16 U.S. patents and has given over 70 technical talks and papers. She is now a professor at Texas A&M University in College Station, TX.