Spatial frequency-based microbending fiber optic sensor

A new approach to fiber optic microbending sensors is demonstrated, where the spatial frequency of the bends, not the amplitude, is varied. This paper shows how to design this sensor, including the effect on sensitivity due to number of bends, bend amplitude, and deformation shape. By prebending the optical fiber into a series of bends, and then embedding it into a compliant material, we created a sensor whose spatial frequency can be changed by compressing the material. Results from our prototype exhibited the predicted transmission loss by alternating bend spacing. Due to the resonant nature of the mode-coupling effect, this modified sensor has the capability of equating to sensitivity levels found in the human finger tip. The application for the quartz industry is to use this sensor to automate those crystal processes which are currently restricted solely to manual means