Whether you believe commercial WDM systems operating at 40 Gbit/s will debut later this year or several years from now, you're probably aware that many companies are vigorously pursuing technologies to make it possible. Dispersion looms as the biggest challenge, and manufacturers are offering a variety of solutions. In our lead article, Alan Willner of Phaethon Communications, addresses the causes and consequences of chromatic dispersion, and methods for compensation. We'll tackle its more difficult sibling, polarization-mode dispersion, later this year. The question lurking behind every technical remedy to dispersion is: Can it be done at a justifiable cost? The answer is not yet clear.
Going faster—and farther—with Raman amplification is the subject of articles by James Passalugo at Corning, and Theodore Mirtchev and Jackson Klein at Optiwave. Passalugo lays out some of the ground rules for designing a high-speed network that incorporates Raman amplification, while Mirtchev and Klein discuss the difficulties involved with standardizing Raman amplifier design because of system variations and how software modeling can help. Marcia Stellflug at Lightwave Electronics completes our coverage of 40-Gbit/s technology with a look at optical receivers, which must be rigorously tested, preferably with optical microwaves from a heterodyne laser system.
It's always satisfying when we can publish several articles illuminating different aspects of the same general subject. The result for the reader is, I trust, the potential for new insight that helps answer design or performance questions. For example, several articles pick up on the amplification theme but focus on erbium-doped fiber amplifiers. Ken Wang and his colleagues at JDS Uniphase write about the advantages of new, more-powerful 980-nm pump laser diodes and how they can be harnessed in creative ways. Atul Srivastava, from startup Onetta, takes a related approach but shows how clever amplifier design can overcome optical-power transients, which are now a concern but could become a major problem as systems become dynamically reconfigurable.
Manufacturing is another subject with multiple angles of approach. Senior editor John Grady, in his "Breaking Bottlenecks" column, discusses how makers of test equipment, in this case Tektronix, must figure out how to manufacture and test their own equipment. Jayson Wilkinson at National Instruments describes the application of machine-vision technology to accurately align fiber. Finally, reflecting the growing importance of optical-microelectromechanical systems (MEMS), we have an article on testing and aligning optical fiber to MEMS switches by Jeff Bonja and Bob Rubino at Schott Communication Technologies, and one by Thomas Cellucci at Etec on systematically testing MEMS devices during high-volume production.
A discussion of any of these technologies leads naturally to thoughts of trade shows and technical sessions to learn more. Fortunately, this is the month for the National Fiber Optic Engineers Conference—see you there!
W. Conard Holton
Associate Publisher/Editor in Chief