Electrooptic modulators that consist of an optical fiber waveguide coupled
to an electrooptic waveguide are reviewed. Desirable attributes of these de
vices are that the optical fiber is uninterrupted and the interaction with
the electrooptic region occurs only where the optical properties are modula
ted. In this paper we review in-line fiber evanescent field modulators that
we have implemented with electrooptic polymers and compound semiconductor
quantum wells. We show that the beam propagation method can accurately simu
late the behavior measured in these devices.