Chapter 1 - Introduction

Abstract

This chapter provides an overview of the fiber characteristics that are important for understanding various non-linear effects. It outlines a historical perspective on the progress in the field of fiber optics. Various fiber properties–– such as, optical loss, chromatic dispersion, and birefringence are also discussed. Under ideal conditions— cylindrical symmetry and a stress-free fiber, a mode excited with its polarization in the x direction would not couple to the mode with the orthogonal y-polarization state. In real fibers, small departures from cylindrical symmetry, occurring because of the random variations in the core shape along the fiber length, result in a mixing of the two polarization states by breaking the mode degeneracy. Particular attention is paid to chromatic dispersion because of its importance in the study of non-linear effects probed by using ultrashort optical pulses. The chapter introduces various non-linear effects resulting from the intensity dependence of the refractive index and stimulated inelastic scattering. Among the non-linear effects that have been studied extensively using optical fibers as a non-linear medium are self-phase modulation, cross-phase modulation, four-wave mixing, stimulated Raman scattering, and stimulated Brillouin scattering. The chapter considers and focuses on non-linear phenonmenon–– namely, SBS, SRS, XPM, GVD, and four wave mixing (FVM)… The chapter concludes by reviewing the various non-linear effects resulting from the intensity dependence of the refractive index and stimulated inelastic scattering.