Abstract

In the past few years there has been considerable effort in the development of all-fiber devices for fiber-optic applications such as optic communication and guidance systems. However, most of these have been passive devices. There exists a need for all-fiber active devices such as modulators, switches, and frequency shifters. For fused silica an electrooptic effect is not applicable. A more effective approach is to use the elastooptic effect. Risk et al.¹ first described a low-frequency amplitude modulator operated at 4.4 MHz using a periodic array of SAW transducers to generate the time-varying coupling. More recently, we reported² a high-frequency device {at 200 MHz) using Bragg diffraction by bulk acoustic waves. In both cases birefringent or polarization-preserving fibers were used. The use of birefringent fibers was considered necessary to satisfy phase matching in the collinear AO interaction; i.e., the spatial modulation along the fiber due to the transducer array¹ or acoustic wave component² must be equal to the beat length of the birefringent fiber.

© 1986 Optical Society of America