Chapter 3 - Fiber interferometers

Abstract

Directional couplers and fiber gratings can be combined to form a variety of fiber-based passive optical devices. Four common ones among them are the fiber version of the well-known Fabry–Perot, Mach–Zehnder, Sagnac, and Michelson interferometers. All of them exhibit interesting nonlinear effects useful for optical-switching applications when power levels are large enough for the nonlinear effects to become relevant. Section 3.1 focuses on the Fabry–Perot and ring resonators and describes several nonlinear effects, such as optical bistability, chaos, and modulation instability, that may occur because of optical feedback. Nonlinear fiber-loop mirrors, whose operation is based on Sagnac interferometers, are covered in Section 3.2. Such devices are commonly employed for switching an optical beam nonlinearly to a different output port by changing the incident power. Both the SPM- and XPM-based switching schemes are discussed in this section, together with their potential applications. Nonlinear switching in Mach–Zehnder interferometers is described in Section 3.3. Finally, Section 3.4 is devoted to Michelson interferometers.