Modulation Instability in Periodically Modulated Fibers

Modulational instability (MI) constitutes one of the most basic and widespread nonlinear phenomena in physics, and it has been studied extensively in several different physical systems such as water waves, plasmas, and optical devices. This chapter introduces the basic theory of MI in periodically modulated fibers, and discusses the fabrication technique of such fibers and their basic optical properties. It develops a general theory that identifies the frequency bands that can be destabilized by a periodic modulation of fiber dispersion or nonlinearity. The chapter presents experimental results highlighting the specific features of the modulation instability process in dispersion oscillating fibers. It utilizes a standard master oscillator power amplifier (MOPA) setup to investigate in detail the modulation instability process in the periodically modulated waveguides. More generally, the modulation of the outer diameter of optical fibers provides a new degree of freedom in nonlinear optics. The chapter investigates the behavior of solitonic pulses propagating in these waveguides.