Contamination of Fresh Produce by Microbial Indicators on Farms and in Packing Facilities: Elucidation of Environmental Routes

Bartz, Faith E. y Lickness, Jacquelyn Sunshine y Heredia, Norma y Fabiszewski de Aceituno, Anna y Newman, Kira L. y Hodge, Domonique Watson y Jaykus, Lee-Ann y García, Santos y Leon, Juan S. y Dozois, Charles M. (2017) Contamination of Fresh Produce by Microbial Indicators on Farms and in Packing Facilities: Elucidation of Environmental Routes. Applied and environmental microbiology, 83 (11). pp. 1-8. ISSN 0099-2240

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Resumen

Abstract: A compact, highly sensitive optical fiber displacement and curvature radius sensor is presented. The device consists of an adiabatic bi-conical fused fiber taper spliced to a single-mode fiber (SMF) segment with a flat face end. The bi-conical taper structure acts as a modal coupling device between core and cladding modes for the SMF segment. When the bi-conical taper is bent by an axial displacement, the symmetrical bi-conical shape of the tapered structure is stressed, causing a changeintherefractiveindexprofilewhichbecomesasymmetric. Asaresult,thetaperadiabaticityis lost, and interference between modes appears. As the bending increases, a small change in the fringe visibility and a wavelength shift on the periodical reflection spectrum of the in-fiber interferometer is produced. The displacement sensitivity and the spectral periodicity of the device can be adjusted by the proper selection of the SMF length. Sensitivities from around 1.93 to 3.4 nm/mm were obtained for SMF length between 7.5 and 12.5 cm. Both sensor interrogations, wavelength shift and visibility contrast, can be used to measure displacement and curvature radius magnitudes. Keywords: fiber optic sensor; modal optical fiber Michelson interferometer; displacementcurvature measurement

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