Sensitivity-Enhanced Strain Sensor Based on Thin-Core Fiber Modal Interferometer Interacted With Tilted Fiber Bragg Grating

A sensitivity-enhanced strain sensor constructed by a 7-mm-long thin-core fiber (TCF) splicing with a 10-mm-long tilted fiber Bragg grating (TFBG) was proposed. The modal interferometer formed by the TCF will interact with the spectrum of the TFBG to form an overlapped spectrum, which will extremely increase the axial strain sensitivity of the TFBG. Experimental results showed that the wavelength shifts of the resonant dip in the overlapped spectra for the applied axial strain have a high sensitivity of 0.67 pm/με. Meanwhile, the proposed sensor has the temperature self-compensation function for the variation of the external temperature simply by measuring the relative wavelength shifts of the Bragg mode of the TFBG.