| The advent of fiber optics has led to an explosion in the performance, reliability, and accessibility of optically-based information services. In addition to the increasing number of traditional data/telephony applications such as communications and data networks, the use of fiber optics has matured beyond its original ground-based implementation, and is now extending into diverse fields ranging from aerial subsystems found in phased-array radar control, to remote sensing applications such as engine performance monitoring, and to undersea exploration in the form of towed sensor arrays.; An all-optical switch is a potentially important component in these fields with uses ranging from packet routing to network reconfiguration. For many applications, currently available devices, including several recently demonstrated, can be too expensive to fabricate and integrate with fibers, have high insertion loss, require on-site electrical power, respond too slowly, or can not operate in harsh environments. This dissertation focuses on the development of an optically-controlled, silica based switching approach, which will be cheaper to make, easier to integrate, and suffer lower insertion loss than current techniques.; Until recently, the potential for silica based nonlinear devices was limited by the weak third-order nonlinearity of undoped silica. Optical switches based upon the Kerr-effect in fibers require long interaction lengths and high peak intensities. We have developed a novel approach that dramatically reduces the power and length requirements for silica based devices by utilizing doped silica fibers, relying on the well-known principle that nonlinearities are enhanced in the vicinity of a resonant dopant. As detailed in this thesis, we have demonstrated a practical, fiber based approach to all-optical switching which can achieve sub-microsecond speeds, but with power requirements that are orders of magnitude lower than comparable Kerr-effect devices.; This dissertation outlines the theoretical principles behind resonant enhancement and addresses the experimental techniques utilized and switching results obtained from several dopants ranging from proof-of-concept studies in erbium and neodymium doped fibers, to radiation induced color centers in phosphorus and zirconium doped fibers, and to transition metals in the form of vanadium doped fiber, with results which should yield devices that are currently commercially unavailable in an all-fiber format. |
