From dromedaries to dispersion compensators
From the Silk Road to the Transcontinental Railroad, the long-haul transport of raw or finished goods has been the great binder of far-flung peoples. Wavelength-division-multiplexing systems have performed a similar feat for the bits and bytes of our world.
This ability to send large quantities of data over great distances on a single fiber—or even a single wavelength—has been continually refined and improved over the last few years. Current and future systems incorporate very narrow channel spacing, FEC, Raman amplification, dispersion compensation, and dynamic capabilities. Gabriel Odeh at Ciena introduces these topics and describes how designers can evaluate them for new networks. Jigesh Patel at RSoft Design Group then picks up on this theme to show how accurate modeling of dispersion-compensation schemes can further improve performance. Finally, Mohammed Islam and Mark Nietubyc at Xtera take a closer look at the possibilities of all-Raman amplification.
Amplification by erbium-doped fiber amplifiers (sometimes in concert with Raman) is now the means by which transmission signals are sent thousands of kilometers. Isabella Jung and Stefan Mohrdiek of Nortel Networks discuss the pump lasers that drive this amplification, and show that the uncooled versions may help amplify shorter, metropolitan spans as well. Given the power requirements on the transmission lasers that first send the signal, electroabsorptive-modulated lasers (EMLs) have become a fixture in 2.5- and 10-Gbit/s systems. As described by Erin Byrne at Agere Systems, EMLs may also do for 40-Gbit/s signals.
Until recently, WDM has been essentially synonymous with long-haul (or ultralong-haul) applications. Metro WDM systems are now attracting considerable interest as carriers seek cost-effective means of delivering services to access providers or directly to end users. Although metro may be the fastest growing application of WDM technology, the largest percentage of time, talent, and investment in WDM will continue to be in long-haul. In fact, I can make the case that the more these metropolitan and access networks are successfully deployed, the greater the demand for long-haul WDM.
Wavelength-division multiplexing, and all of optical networking, is not just a series of black boxes connected by long strands of fiber. Engineers, managers, entrepreneurs, investors, and end users of all sorts across the globe are connected. Through the products they design and build, the services they provide or, in the case of children, maybe the cybergames they play, all of us are linked. I can think of no better place to witness the diversity and common bonds than at the Optical Fiber Communications Conference in Anaheim, CA, March 17-22. See you there!
W. Conard Holton
Associate Publisher/Editor in Chief