Highly Strain and Bending Sensitive Microtapered Long-Period Fiber Gratings

Abstract

A microtapered long-period fiber grating (MTLPFG) is fabricated successfully by periodically tapering a standard single-mode fiber with CO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> laser heating source. This can be done by taking advantage of that the effective index difference between the core mode and the cladding modes is changed periodically during microtapering. High fabrication reproducibility and MTLPFGs quality can be achieved by this CO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> laser-heater-based fabrication scheme. In addition, the strain, bending, and liquid-level sensing characteristics of the MTLPFGs are investigated experimentally. Compared with the conventional long-period fiber gratings, it is found that the strain and bending sensitivities of fabricated MTLPFGs are improved by factors of about 10 and 5, respectively. Considering the simple and flexible fabrication process as well as the high quality and sensitivity of fabricated MTLPFGs, we believe that this may offer a simpler and alternative choice to current filters or sensing applications.