Optical EngineeringNew approach to microbending fiber optic sensors: varying the spatial frequency
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A new approach to fiber optic microbending sensors is demonstrated, in which the spatial frequency of the bends, rather than of the amplitude, is varied. This scheme has the potential for greatly increased sensitivity, greater flexibility of design, and longer lifetime. The fiber is prebent and embedded in a compliant material, and the spatial frequency is chosen to bias the sensor on the steep slope of the resonance in the loss curve. Compression in the longitudinal direction causes a dramatic change in the transmission. Sensitivity depends on the resonance slope, which is controlled by bend number, bend shape, and bend amplitude. In conventional microbend sensors, friction and abrasion severely limit the number of bends, and the maximum bend amplitudes and bend shapes cannot be controlled. In the new approach, all three parameters can be independently controlled, resulting in greater design flexibility,high sensitivity, and a long sensor life.