TABLE OF CONTENTS Highly focused coherent laser light, propagating with low loss through optical fiber over long distances (kilometers), is an ideal breeding ground for nonlinear interaction with the glass material. Although nonlinear effects were found in early optical transmission work with analog signal delivery (CATV, etc.), much attention lately has been given to resolution of nonlinear problems in long-haul optical communications and high-power operation in specialty fibers. In particular, new fiber types have been developed to overcome nonlinear impairments. As fiber design introduced dispersion-shifted fibers (DSFs) in the early 1990s, to overcome chromatic dispersion impairments, it was soon found that multiple lightwaves, with different wavelengths, were able to efficiently interact through a four-wave mixing (FWM) process since the coupling waves were well matched in phase and group velocity. This led to the development of NZDFs that struck a balance between the high chromatic dispersion of standard single-mode fiber and the very low dispersion, at operating wavelengths, of DSFs. With the advent of high-power erbium-doped fiber amplifiers (EDFAs) and high-power laser diodes, many nonlinear issues arose because of the long distance between signal regeneration points and the multiple optical wavelengths that could simultaneously be used. In particular, stimulated Brillouin scattering became apparent (at 5-10 dBm levels with laser line widths <5 MHz). This required new features in transmitters to broaden the effective source line width. Self- and cross-phase modulation issues were also noted. Generally, these problems increased with small effective area fibers (such as those...
