Traditionally, modal dispersion in multimode fiber has limited the bit rate-distance product to less than about 2 Gbit/s-km. Models for modal dispersion must take account of mode coupling by fiber imperfections and bends. In the past, mode coupling has been studied using a power-coupling model. However, this model is inherently unable to describe some effects in high-speed links using coherent laser sources, such as polarization dependence of impulse response. In this book, we describe a field coupling model for propagation in MMF, which is analogous to the model used to study...