  Tunable photonic elements at the surface of an optical fiber with
piezoelectric core are proposed and analyzed theoretically. These elements are
based on whispering gallery modes whose propagation along the fiber is fully
controlled by nanoscale variation of the effective fiber radius, which can be
tuned by means of a piezoelectric actuator embedded into the core. The
developed theory allows one to express the introduced effective radius
variation through the shape of the actuator and the voltage applied to it. In
particular, the design of a miniature tunable optical delay line and a
miniature tunable dispersion compensator is presented. The potential
application of the suggested model to the design of a miniature optical buffer
is discussed.
