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Stimulated Brillouin scattering(sBs) is the most dominant nonlinear process in optical fibers. It is a laser induced acousto-optic phenomenon with inherent optical feedback. As such, it is inherently quasi-periodic and chaotic in nature. The critical factors of fiber length, power, and feedback work together in producing this complex behavior. The Brillouin Fiber Ring greatly reduces the SBS linewidth as opposed to the open-ended scheme on the one hand, but enhances nonlinear dynamical instabilities such as quasi-periodicity and chaos. There is a rich variety of temporal behavior that flows through a seemingly automatic process of change above threshold. Increasing input power causes the dynamical behavior to further change while for some powers induces a change in line position or creates multiple lines in the frequency domain. The origin of these instabilities is being studied, while developing a means to suppress them.

Nonlinear fiber optics, in the form of stimulated Brillouin scattering (SBS), has now emerged as the essential means for the construction of active optical devices used for all-optic in-line switching, channel selection, amplification, oscillation in optical communications, optical logic elements in optical computation and sensing, and a host of other applications. This paper attempts to present a survey and some of our own research findings on the nature of stimulated Brillouin scattering in single mode optical fibers and its device applications. In theory, the backscattering nature of the phenomenon enables its application as channel selectors and switches and filters in optical transmission and communications. We have been engaged in the design and implementation of fiber configurations, such as rings and loop mirrors, with the purpose of lowering the threshold. We report on experimental schemes involving Brillouin ring with amplifier-in-the ring, and Brillouin-NALMs (nonlinear amplifying loop mirrors). These successful devices are being studied for application as optical logic and neuron elements, Brillouin-NALMs for optical switching, and highly versatile sensors.

We have studied stimulated Brillouin scattering in single-mode optical fibers as a sensor for both temperature and strain. Shape Memory alloy Nitinol is also studied for enhancement of active sensing and control in structures. We have introduced the hybrid sBs amplifier/oscillator scheme, in which the short fiber amplifier performs sensing and the long oscillator fiber provides the required signal. The sensing fiber can be coated with SMA thin film for ruggedness, increased sBs sensitivity to temperature and strain, and memory or trainability. The oscillator/amplifier scheme also serves as a building block in the design of optical threshold logic circuits, optical computation, and more sophisticated sensing schemes. Such sensing schemes can be highly competitive with those based on fiber Bragg grating. The incorporation of SMA thin films provides memory capability to all these applications.