High-sensitive optical force sensor based on enhanced effective index modulation

A high-sensitive force sensor with large measurement range has been realized by inserting a microbend at the edge of a long period fiber grating (LPFG) written on single-mode fiber. The force sensitivity is improved mainly dependent on the enhanced effective index modulation. Experiment results present that the resonance dip wavelength of the proposed grating varies with applied axial force in an approximate exponential functional manner, and the grating with lower bending radius microbend has higher force sensitivity. A maximum arithmetic mean value of force response ∼−41.24 nm/N is achieved by a microbend edge-inserted grating with a bending radius 1.14 mm, which is almost two order enhanced than that of the original LPFG. In addition, the power-referenced sensitivity is almost a hundred times larger than that of the original LPFG in a certain measurement range. The sensor enables double demodulation of wavelength and energy and is a candidate for force sensors.