A Miniature Fiber Collimator for Highly Sensitive Bend Measurements

A Fabry-Perot interferometer (FPI) composed of a miniature fiber collimator is proposed and demonstrated for high-sensitivity bend measurements. The device consists of a quarter-pitch graded index fiber (GIF) spliced with a section of silica tube, which is interposed between single-mode fibers. The divergence angle of the included miniature fiber collimator was 0.058 rad, which was found to enhance the sensitivity of the proposed FPI to -3.353 dB/degree over the applied angle range. In comparison, the divergence angle without the collimator was 0.130 rad and FPI sensitivity was -0.618 dB/degree over the applied angle range. The fiber bend sensors demonstrated in this paper are compact, robust, and highly sensitive, and hence, are promising in various biomedical applications.