Pulse Propagation in Fibers

This chapter focuses at obtaining a basic equation that governs the propagation of the optical pulses in the single-mode fibers. It reviews the Maxwell's equations and concepts such as—the linear and non-linear parts of the induced polarization and the frequency-dependent dielectric constant. The concept of fiber modes with the single-mode condition is also discussed. The two orthogonally polarized modes of a single-mode fiber are degenerate; that is, they have the same propagation constant under ideal conditions. Polarization-preserving fibers can maintain the linear polarization if the light is launched with its polarization along one of the principal axes of the fiber. The characterstics of fundamental mode are illustrated graphically as well as numerically. The chapter derives a basic equation that governs propagation of optical pulses in non-linear dispersive fibers, “pulse-propogation equation.” Various numerical techniques for studying the pulse-propagation problem in optical fibers with emphasis on the split-step Fourier method and its modifications are also discussed in the chapter's conclusion.