ABSTRACT
Many optical communication networks integrate optical switches into their design. Optomechanical switches redirect optical signals from one port to another by moving a fiber tube assembly or an optical component, such as a mirror or prism. There are many different types of optical switches incorporated into networks. In practice, most optical switches are still operated mechanically and controlled by an electronic control circuit. Switches with no moving parts can be built by using some of the passive devices, such as Mach-Zehnder interferometers and couplers. Some optical materials, such as lithium niobate crystal, Avalanche Photo Diode, and KDP, exhibit an electro-optic effect. A similar coupler may be made by timed etching of the fibers. Hydrofluoric acid may be used to remove as much cladding as desired; this exposes the core and produces an evanescent field. Within the etched regions, fiber-to-fiber optical coupling will occur for fibers placed in close proximity.
