D.O. Culverhouse

The acousto-optic effect in single-mode fiber tapers and couplers

All-fiber acousto-optic devices based on the null fused taper coupler have been successfully demonstrated as frequency shifters, variable splitters, switches and tunable filters. In this paper, the interaction upon which these devices are based has been extensively analyzed under a set of approximations that are valid in most cases. Simple analytical expressions for the important properties are derived, which provide a set of design rules for such devices.

Theory of forward stimulated Brillouin scattering in dual-mode single-core fibers

Recently, stimulated Brillouin scattering in a forward direction (FSBS) in a dual-mode single-core optical fiber was reported by the authors (see Electron Lett., vol.26 p.1195-6, 1990). Frequency shifts on the order of 17 MHz were seen in fiber supporting LP/sub 01/ and LP/sub 11/ modes at 514.5 nm. The phenomenon is examined in detail, and the governing differential equations of the three-wave parametric process, (involving laser pump, Brillouin signal, and acoustic flexural-wave phonon) are derived and solved. FSBS is possible because although the overlap integral between a flexural fiber mode and the light is small, the phonon lifetime is much longer than in conventional stimulated Brillouin scattering (SBS). FSBS may also be the first example of a nonlinear effect which is enhanced by increasing the optical model area at constant pump power. >