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Abstract: A simple fiber-optic sensor based on Fabry–Perot interference for small displacement measurement is investigated both theoretically and experimentally. A broadband light source is coupled into a Fabry–Perot cavity formed by the surfaces of a sensing fiber end and the measured object. The interference signals from the cavity are reflected back into the same fiber. A small displacement via changes in cavity length can be obtained by measuring the wavenumber spacing of the interference fringes. The experimental data meet with the theoretical values very well. Given the light source bandwidth of 40nm and the initial distance of 30μm, the proposed displacement sensing system could achieve high resolution measurement of 16nm. [Copyright &y& Elsevier]

Abstract: All-optical broadband variable optical attenuators (VOAs) and switches based on plasmonic teeth shaped waveguides have been proposed and numerically investigated. The Finite Difference Time Domain (FDTD) simulation results reveal that VOAs based on three teeth structure filled with CdSe-doped PMMA can continuously attenuate the power of a light beam from 3.7dB to 39dB within a broad forbidden band by an external control light. For wavelengths within the forbidden band, the structure can also operate as a switch with presence or absence of pumping light corresponding to on or off state. For a modulation depth of 27dB, a relatively small variation in the absorption coefficient of CdSe QD-PMMA in side cavity (from κ= 0 to κ= 0.15) is enough. [Copyright &y& Elsevier]