This paper presents a pre-biased fiber optic microbending sensor where perturbation is based on the number of microbends rather than the bending amplitude. The sensor uses a graded index fiber where a portion of the fiber is pre-bent to bias the sensor precisely at the peak of the loss curve. This can be achieved by matching the bending period of the pre-bent fiber to the resonance spatial frequency of the fiber itself. In principle, the sensor operates based on the conventional microbending sensing schemes, however, the emphasis on the bending amplitude is relaxed to prevent the rapid degradation of the fiber and to prolong the sensor lifetime. It also is shown that the proposed sensor shows higher sensitivity than the amplitude based sensor.
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