Acoustic velocity and attenuation were measured in poled and unpoled lead zirconate titunate (PZT) ceramics prepared by sintering and hot-pressing under different conditions. Hot-pressed PZT was found to have attenuation vdues approximately I order of magnitude smaller than sintered PZT. For both materials, poling cliused a decrease in attenuation. Depolurization and phase transition phenomena were also observed at elevated temperatures using a novel laserultrasound technique in combination with conventional pulse-echo measurements.

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An all-fiber spectral filter constructed with step-index and W-type fibers is proposed. A coupled-mode theory based on the interaction of evanescent fields is employed to analyze the transfer of power between the two fibers. The proposed filter on'ers a narrow spectral width on the order of few nanometers. The narrow bandwidth is achieved by exploiting a relatively large slope din'erence between the dispersion characteristics of the step-index and W fibers. Transmission characteristics are plotted versus wavelength. The influence of various fiber parameters as well as fiber separation and coupling length on the spectral response is discussed. The application o f t h e filter in wavelength division multiplexing is addressed.