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Experimental and theoretical results on the nonspecular reflection of finite acoustic beams incident at and near the Rayleigh angle onto a fluid-solid interface loaded by an elastic layer are presented. Measurements with Gaussian-shaped acoustic beams have been performed on the reflected field amplitude distribution and surface wave speed dispersion in copper-loaded stainless-steel specimens where the fluid medium is water. It is shown that existing theory can be utilized to explain the results by constructing and solving boundary condition equations for the Rayleigh wave pole appropriate for the lossless layered halfspace with the fluid. Excellent agreement with the exact treatment is observed in most aspects of the measurements. In the model calculation the imaginary part of the Rayleigh wave pole is found to display an unexpected maximum at a value of layer thickness over wavelength where the real part corresponds nearly to the transverse wave speed in the layer.

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Using a fiber-optic stimulated-Brillouin-scattering amplifier as an active filter, we have demonstrated optical clock recovery from 5-Gbit/s return-to-zero-format optical data. Definite patterns and pseudorandom bit sequences were tested. This scheme requires no prior knowledge of the clock frequency and is well suited for operation at higher data rates.