Atmospheric turbulence over long horizontal paths perturbs phase and can also cause severe intensity scintillation in the pupil of an optical communications receiver, which limits the data rate over which intensity-based modulation schemes can operate. The feasibility of using low-order adaptive optics by applying phase-only corrections over horizontal propagation paths is investigated. A Shack-Hartmann wave-front sensor was built and data were gathered on paths 1 m above ground and between a 1- and 2.5-km range. Both intensity fluctuations and optical path fluctuation statistics were gathered within a single frame, and the wave-front reconstructor was modified to allow for scintillated data. The temporal power spectral density for various Zernike polynomial modes was used to determine the effects of the expected corrections by adaptive optics. The slopes of the inertial subrange of turbulence were found to be less than predicted by Kolmogorov theory with an infinite outer scale, and the distribution of variance explained by increasing order was also found to be different. Statistical analysis of these data in the 1-km range indicates that at communications wavelengths of 1.3 mum, a significant improvement in transmitted beam quality could be expected most of the time, to a performance of 10% Strehl ratio or better.

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With their simple geometries and capabilities for system integration, planar resonators have attracted considerable interest for microelectronics and microwave circuit applications. Together with MEMS technology and smart materials, they have been used on telecommunications, radio frequency identification, remote sensing, etc. The design of these devices is complicated by many conflicting requirements that must be taken into account. Often, researchers are compelled to carry out complex numerical computations and trial-and-error experiments to achieve acceptable performances. This paper reports on a multi-objective optimization method employed in the design of a planar resonator used as a passive wireless strain sensor. The technique can provide designers with a systematic and efficient approach to achieve the optimization of the geometry of the device based on the application requirements. Numerical results from nonlinear programming are shown and tradeoffs are discussed.