area around 50 um ². The Corning Vascade L1000 fiber offers an effec- tive area of 101 um2 2 Looking at research results, a fiber design using a novel approach claims an effective area of 1470 um2 2 (Wong et al., 2005). System design with optical nonlinearities present is a complex undertaking and after some preliminary calculations one has to use a simulation package that solves the nonlinear propagation equation (nonlinear Schrödinger equation) under the conditions imposed the system details. A good introduction is given in Agrawal (2005). Future Evolution of Optical Fiber Communications Silica glass proved to be the ideal material in its optical and mechanical properties and also for manufacturing cabling and reliability. The losses have been reduced to such an extent that any further progress in that direction will be met with the law of diminishing returns. There has been work on new glass materials whose intrinsic theoretical losses are less than that of silica. They are collectively referred to as telluride and fluoride glasses. Figure 5.31 shows the theoretical loss spectrum of these glasses. The interesting aspect of these losses is that, at the wavelengths where optical fiber systems operate now, silica glass is still as good as or better than these new glasses. There- fore, to exploit the theoretical low fluoride losses, the optical window has to shift to longer wavelengths. Here semiconductor optical devices will have difficulties delivering the performance one has come to expect in the and L-bands and around 1300 nm. In spite of the theoretical low losses, experimental work with fluoride material has not delivered Chapter 5 Optical Fibers Telluride Silica Glass Glass Fluoride Ultraviolet Glass Absorption Rayleigh Scattering Infrared Absorption Fig. 5.31 Theoretical performance of some potential new fiber materials. Source: FibreLabs, Inc. Used with permission. Wavelength (nm) results that will give confidence for the future. Therefore, from the material perspective, silica glass will continue to domi